Targeted Airstrikes Against the Islamic State of Iraq and the Levant

                Targeted Airstrikes Against the Islamic
                     State of Iraq and the Levant
The President had the constitutional authority to order targeted airstrikes in Iraq against
  the Islamic State of Iraq and the Levant without prior congressional authorization.
The President had reasonably determined that these military operations would further
  sufficiently important national interests. A combination of three relevant national in-
  terests—protecting American lives and property; assisting an ally or strategic partner
  at its request; and protecting endangered populations against humanitarian atrocities,
  including possible genocide—supported the President’s constitutional authority to
  order the operations without prior congressional authorization.
The anticipated nature, scope, and duration of the military operations did not rise to the
  level of a “war” within the meaning of the Declaration of War Clause.

                                                                      December 30, 2014

     MEMORANDUM OPINION FOR THE COUNSEL TO THE PRESIDENT

   On August 8, 2014, United States Armed Forces commenced targeted
airstrikes in Iraq against the terrorist group the Islamic State of Iraq and
the Levant (“ISIL”). Before the strikes began, our Office advised you that
the President had the constitutional authority to order these military
operations because he had reasonably determined that they would further
sufficiently important national interests, and because their anticipated
nature, scope, and duration were sufficiently limited that prior congres-
sional approval was not constitutionally required. This memorandum
memorializes and explains the basis for our advice. 1


   1 This advice was provided before the President decided to rely on statutory authority

for military operations against ISIL. We accordingly do not address in this opinion
whether the targeted military actions discussed herein were authorized by any statute. We
further note that on September 10, 2014, after the advice memorialized in this opinion had
already been provided, the President announced a new “comprehensive and sustained
counterterrorism strategy” to address the threat posed by ISIL that, among other things,
called for a “systematic campaign of airstrikes” against the organization in Iraq and, if
necessary, Syria. Office of the Press Secretary, The White House, Statement by President
Obama on ISIL (Sept. 10, 2014), https://obamawhitehouse.archives.gov/the-press-office/
2014/09/10/statement-president-isil-1. You have not asked us to consider in this opinion,
and we do not address, the President’s authority to implement this new strategy. We also
do not consider whether the discrete military operations discussed in this opinion would

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         Targeted Airstrikes Against the Islamic State of Iraq and the Levant

                                           I.

   The conflict that led to the airstrikes discussed in this opinion has its
origins in the most recent Iraq War. In 2002, in response to concerns that
Saddam Hussein’s regime might be developing and stockpiling weapons
of mass destruction and aiding and harboring terrorists, Congress author-
ized the President to use military force against the threat posed by Iraq.
See Authorization for Use of Military Force Against Iraq Resolution of
2002, 

 Stat. 1498 (“Iraq AUMF”); Raymond W.
Copson, Cong. Research Serv., RL31715, Iraq War: Background and
Issues Overview 1–2 (Apr. 22, 2003) (“Iraq War: Background and Issues
Overview”). On March 19, 2003, after diplomatic efforts to resolve these
concerns failed, the United States began aerial attacks in Iraq. See Iraq
War: Background and Issues Overview at 4. U.S. and British ground forces
entered Iraq the next day, 

 and several weeks later, Saddam Hussein’s
regime fell, Kenneth Katzman, Cong. Research Serv., RS21968, Iraq:
Politics, Governance, and Human Rights 1 (Aug. 12, 2014) (“Iraq: Poli-
tics, Governance, and Human Rights”). After the fall of the regime, a new
Iraqi government was formed, and U.S. and other coalition forces re-
mained in Iraq to help secure and stabilize the country. See 

 Over the
next few years, however, as sectarian divisions in Iraqi society deepened,
see 

, the terrorist group Al-Qaeda in Iraq—Al-Qaeda’s affiliate in
Iraq and the primary source of armed opposition to the new Iraqi gov-
ernment and U.S. forces—intensified its operations and expanded its
reach, see Kenneth Katzman, Cong. Research Serv., RL32217, Al Qaeda
in Iraq: Assessment and Outside Links 1, 10–11 (Aug. 15, 2008); Bradley
Graham, Zarqawi “Hijacked” Insurgency, Wash. Post, Sept. 28, 2005, at
A17. In 2006, Al-Qaeda in Iraq renamed itself the Islamic State of Iraq
(“ISI”). See Kenneth Katzman et al., Cong. Research Serv., R43612, Iraq
Crisis and U.S. Policy 8 (Aug. 8, 2014) (“Iraq Crisis and U.S. Policy”).
Violence continued to escalate and, by early 2007, had become wide-
spread and severe. See Nominations Before the Senate Armed Services
Committee: Hearings Before the S. Comm. on Armed Servs., 110th Cong.
5–8 (2007) (statement of Lt. Gen. David H. Petraeus). The United States

have been within the President’s constitutional authority if they had been ordered pursu-
ant to the newly announced strategy, rather than for the more limited missions for which
they were actually ordered.

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responded with a surge of nearly 30,000 troops. See Iraq: Politics, Gov-
ernance, and Human Rights at 4. Over the course of 2007 and 2008, in
the wake of the surge, sectarian violence in Iraq dropped dramatically.
See Stephen Biddle et al., Testing the Surge: Why Did Violence Decline
in Iraq in 2007?, 37 Int’l Sec. 7 (Summer 2012).
   In 2008, the United States and Iraq signed a Strategic Framework
Agreement for a Relationship of Friendship and Cooperation Between the
United States of America and the Republic of Iraq (“Strategic Framework
Agreement” or “Agreement”), which recognized that cooperation between
the two countries would “improve and strengthen security and stability in
Iraq and the region.” Strategic Framework Agreement at 2 (Nov. 17,
2008), https://www.state.gov/documents/organization/122076.pdf. Among
its many provisions, the Agreement stated that the United States and Iraq
would “continue to foster close cooperation concerning defense and
security arrangements without prejudice to Iraqi sovereignty over its land,
sea, and air territory.” 

. The United States began to reduce its mil-
itary presence in Iraq in 2009, and in December 2011, the last U.S. troops
left the country. See Iraq: Politics, Governance, and Human Rights at 8;
Tim Arango & Michael S. Schmidt, Last Convoy of American Troops
Leaves Iraq, Marking a War’s End, N.Y. Times, Dec. 19, 2011, at A6. In
announcing this withdrawal, President Obama explained that the United
States was “moving into a new phase in [its] relationship” with Iraq, “an
equal partnership based on mutual interests and mutual respect.” Office
of the Press Secretary, The White House, Remarks by the President on
Ending the War in Iraq (Oct. 21, 2011), https://obamawhitehouse.
archives.gov/the-press-office/2011/10/21/remarks-president-ending-war-
iraq.
   After U.S. military forces had left Iraq in 2011, the long-standing sec-
tarian and ethnic divisions in the country again widened, leading to in-
creased discontent and unrest. See Iraq: Politics, Governance, and Human
Rights at 15–19. During this period, Sunni extremists, including ISI,
gained strength. See 

 In April 2013, after having expanded into Syria,
ISI adopted the name ISIL. 2 See Iraq Crisis and U.S. Policy at 8, 11. ISIL

   2 ISIL is also sometimes referred to as the “Islamic State of Iraq and Syria,” or “ISIS.”

This opinion refers to the group as “ISIL” hereafter, including in references to the group
following its decision to change its name to the “Islamic State.” See infra p. 86.

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

soon launched a series of attacks in Iraq. See 

 at 7–9. In December
2013, aided by Sunni citizens and tribal fighters dissatisfied with the
failure of Iraq’s Shiite-dominated leadership to create an inclusive gov-
ernment, ISIL attacked the Iraqi cities of Ramadi and Fallujah, ultimately
gaining control of Fallujah despite an Iraqi counteroffensive. See Iraq:
Politics, Governance, and Human Rights at 18. Then, in June 2014, ISIL
launched a major offensive in Iraq and, assisted by the widespread surren-
der and withdrawal of the Iraqi Security Forces (“ISF”) and an influx of
fighters from Syria, captured Mosul, Iraq’s second largest city, and large
areas of the provinces of Nineveh and Salahuddin. See 

; Rod
Nordland, Sunnis in Iraq Make Some Gains in Fighting in the North and
West, N.Y. Times, June 22, 2014, at A7. ISIL militants thereafter rapidly
expanded their control over northwestern areas of Iraq, capturing key
cities and attacking Iraq’s largest oil refinery. See Iraq: Politics, Govern-
ance, and Human Rights at 19–20. Within a week of Mosul’s fall, ISIL
reached the outskirts of Baquabah, thirty-eight miles from Baghdad,
prompting fear that the capital too would fall. See Iraq Crisis and U.S.
Policy at 1. ISIL militants also advanced toward the Haditha Dam, situat-
ed about 120 miles northwest of Baghdad on the Euphrates River, raising
the prospect of catastrophic flooding if the dam were to fail. See Alissa J.
Rubin & Rod Nordland, As Calls for New Iraqi Government Grow, Mili-
tants Advance Toward Strategic Dam, N.Y. Times, June 25, 2014, at A10.
In the course of its advance, ISIL looted banks of millions of dollars,
seized a substantial amount of U.S.-supplied military equipment, and
freed prisoners. See Iraq Crisis and U.S. Policy at 1. Its tactics were
brutal: it executed innocent civilians, performed mass executions of ISF
members, kidnapped and raped women and children, and displaced hun-
dreds of thousands of Iraqis from their homes. See Office of the High
Commissioner for Human Rights & U.N. Assistance Mission for Iraq
(UNAMI) Human Rights Office, Report on the Protection of Civilians in
the Non-International Armed Conflict in Iraq: 5 June–5 July 2014, at 7–
13, https://www.ohchr.org/Documents/Countries/IQ/UNAMI_OHCHR_
POC%20Report_FINAL_18July2014A.pdf.
   In remarks on June 19, 2014, President Obama declared ISIL “a threat
to the Iraqi people, to the region, and to U.S. interests.” Office of the
Press Secretary, The White House, Remarks by the President on the
Situation in Iraq (June 19, 2014), https://obamawhitehouse.archives.gov/

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the-press-office/2014/06/19/remarks-president-situation-iraq. He stated
that “[i]t is in [the] national security interests [of the United States] not to
see an all-out civil war inside of Iraq,” and to “mak[e] sure that we don’t
have a safe haven” in Iraq “that continues to grow for ISIL and other
extremist jihadist groups who could use that as a base of operations for
planning and targeting ourselves, our personnel overseas, and eventually
the homeland.” 

 The President then announced that he had positioned
additional U.S. military assets in the region and “w[ould] be prepared to
take targeted and precise military action” if and when he determined that
“the situation on the ground require[d] it.” 

 In light of the growing
threat from ISIL, the President also dispatched U.S. military personnel to
Iraq three times in June to, among other things, provide support and
security for U.S. embassy personnel in Baghdad and establish joint
operations centers with Iraqi forces. 3
   On June 29, ISIL changed its name to the “Islamic State” and declared
that it had established an Islamic “caliphate” extending from the Aleppo
province in Syria to the Diyala province in Iraq. Iraq Crisis and U.S.


   3 See Office of the Press Secretary, The White House, Text of a Letter from the Presi-
dent to the Speaker of the House of Representatives and the President Pro Tempore of the
Senate (June 16, 2014), https://obamawhitehouse.archives.gov/the-press-office/2014/06/
16/text-letter-president-speaker-house-representatives-and-president-pro-te (authorizing
the deployment of 275 troops “to provide support and security for U.S. personnel and the
U.S. Embassy in Baghdad”); Office of the Press Secretary, The White House, Letter from
the President—War Powers Resolution Letter Regarding Iraq (June 26, 2014), https://
obamawhitehouse.archives.gov/the-press-office/2014/06/26/letter-president-war-powers-
resolution-letter-regarding-iraq (authorizing the deployment of 300 additional troops “to
assess how we can best train, advise, and support Iraqi security forces and to establish
joint operations centers with Iraqi security forces to share intelligence and coordinate
planning to confront the threat posed by ISIL”); Office of the Press Secretary, The White
House, Letter from the President—War Powers Resolution Letter Regarding Iraq (June
30, 2014), https://obamawhitehouse.archives.gov/the-press-office/2014/06/30/letter-
president-war-powers-resolution-letter-regarding-iraq (authorizing the deployment of 200
additional troops “to reinforce security at the U.S. Embassy, its support facilities, and the
Baghdad International Airport”). In early September, the President authorized the de-
ployment of an additional 350 U.S. military personnel “to provide support and security for
U.S. personnel and the U.S. Embassy in Baghdad.” Office of the Press Secretary, The
White House, Letter from the President—War Powers Resolution Regarding Iraq (Sept. 5,
2014), https://obamawhitehouse.archives.gov/the-press-office/2014/09/05/letter-president-
war-powers-resolution-regarding-iraq.

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

Policy at 8. The declaration named ISIL’s leader Abu Bakr al Baghdadi as
Imam and “[C]aliph.” 

 In territories they controlled, ISIL militants
intensified a campaign of persecution against non-Sunni religious groups
and ethnic minorities, including Shiites, Christians, and Yezidis, an an-
cient and long-persecuted religious sect. See Alissa J. Rubin, ISIS Expels
Last Iraqi Christians from Mosul, N.Y. Times, July 19, 2014, at A4;
Loveday Morris, Islamic State Forces Take an Iraqi Town, Wash. Post,
Aug. 4, 2014, at A9; Press Statement, Office of Press Relations, U.S.
Dep’t of State, ISIL Claims Massacre in Tikrit (June 15, 2014) (“State
Department June 15 Press Statement”), https://2009-2017.state.gov/r/pa/
prs/ps/2014/06/227605.htm. Journalists reported that when ISIL militants
swept through Sinjar, a town in northwestern Iraq with a large Yezidi
population, they “set about their method of conquest, which is as familiar
as it is brutal: They destroyed a Shiite shrine, executed resisters, overran
local security forces and hoisted the black flag of [ISIL] above govern-
ment buildings.” Tim Arango, Sunni Extremists in Iraq Seize 3 Towns
From Kurds and Threaten Major Dam, N.Y. Times, Aug. 4, 2014, at A7.
Yezidi residents reported witnessing kidnappings and executions of mem-
bers of their sect. See 

 Tens of thousands of residents fled to the north-
ern Kurdish region of Iraq, while thousands of others, largely from the
Yezidi community, sought refuge on Mount Sinjar, where they were
besieged by ISIL militants. See Alissa J. Rubin, For Refugees on Moun-
tain, “No Water, No Nothing,” N.Y. Times, Aug. 10, 2014, at A1. Those
trapped on the mountain confronted a choice between descending into
areas controlled by the militants and facing likely death, or remaining on
the mountain without sufficient food, water, or medicine. See Loveday
Morris, Cornered on Mountain, Minority-Sect Iraqis Are Dying of Thirst,
Wash. Post, Aug. 6, 2014, at A10. The U.N. Special Representative of the
Secretary-General for Iraq warned that “[a] humanitarian tragedy [wa]s
unfolding in Sinjar.” UN News Centre, UN Warns of “Humanitarian
Tragedy” as Militants Seize Town in Northern Iraq (Aug. 3, 2014); see
also Security Council, Press Statement on Iraq, U.N. Press Release
SC/11509 (Aug. 5, 2014) (“Security Council August 5 Press Release”)
(expressing “deep concern” about the thousands of Iraqis, many from the
Yezidi community, displaced by ISIL and “in urgent need of humanitarian
assistance”). Days after the siege on Mount Sinjar began, the U.N. Securi-
ty Council “call[ed] on the international community to support the Gov-

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ernment and people of Iraq and to do all it c[ould] to help alleviate the
suffering of the population affected by the current conflict in Iraq.” Secu-
rity Council, Press Statement on Iraq, U.N. Press Release SC/11515 (Aug.
7, 2014) (“Security Council August 7 Press Release”).
   By early August 2014, ISIL militants had seized control of additional
towns in northern Iraq and were advancing towards the city of Erbil,
where numerous American diplomats, military advisers, and other citi-
zens were based. See Helene Cooper et al., Obama Allows Airstrikes
Against Iraq Rebels, N.Y. Times, Aug. 8, 2014, at A1; Iraq: Politics,
Governance, and Human Rights at 19. ISIL militants had also seized
control of the Mosul Dam, Iraq’s largest, from Kurdish forces. See Tim
Arango, Jihadists Rout Kurds in North and Seize Strategic Iraqi Dam,
N.Y. Times, Aug. 8, 2014, at A1 (“Jihadists Rout Kurds”). ISIL’s seizure
of the Mosul Dam raised concerns because, as a 2007 report by the Army
Corps of Engineers explained, the Mosul Dam rests on a “very poor”
foundation of water-soluble rock and soil and therefore “demand[s]
extraordinary engineering measures to maintain” its “structural integrity
and operating capability.” Julie R. Kelley et al., U.S. Army Corps of
Engineers, ERDC TR-07-10, Geologic Setting of Mosul Dam and Its
Engineering Implications 2 (Sept. 2007) (“Geologic Setting of Mosul
Dam”). Consistent with that report, the United States had advised Iraq
that an extensive grouting program should be continued to “mitigat[e] the
risk at Mosul Dam,” explaining that “a catastrophic failure” of the dam
would “result in flooding along the Tigris River all the way to Baghdad,”
and, in a worst case scenario, “a f lood wave 20 meters [65 feet] deep at
the city of Mosul,” threatening “significant loss of life and property.”
Letter for Nouri al-Maliki, Prime Minister, Republic of Iraq, from Gen-
eral David H. Petraeus, U.S. Army, and Ambassador Ryan C. Crocker,
United States Embassy, Baghdad (May 3, 2007), reprinted in Office of
the Special Inspector General for Iraq Reconstruction, Relief and Recon-
struction Funded Work at Mosul Dam, SIGIR PA-07-105, app. D (Oct.
29, 2007) (“Mosul Dam Letter”). A later article by an Army Corps offi-
cial estimated that the dam’s failure “could lead to as many as 500,000
civilian deaths by inundating the cities of Mosul and Baghdad under
water.” Amanda Ellison, An Unprecedented Task, 63 Int’l Water Power
& Dam Construction 50, 50–51 (Sept. 2011).


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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

   ISIL militants also continued to battle ISF and allied tribal forces for
control of the Haditha Dam. See Jihadists Rout Kurds, N.Y. Times,
Aug. 8, 2014, at A1. According to press accounts, releasing water from or
destroying that dam could unleash walls of water that could travel hun-
dreds of miles down the Euphrates River, cripple the electricity supply in
Iraq, and potentially flood the southern regions of Baghdad. See Nigel
Wilson, Middle East Water Wars: Why Islamic State Wants Iraq’s Dams,
Int’l Bus. Times, Aug. 5, 2014, https://www.ibtimes.co.uk/middle-east-
water-wars-why-islamic-state-wants-iraqs-dams-1459895; Doug Struck,
The Coolest Posting in a Hot War Zone, Wash. Post, Aug. 8, 2004, at
A17.
   In response to these developments (and subsequent developments de-
scribed below), the United States began a series of targeted airstrikes
against ISIL positions in Iraq, each directed at either protecting Ameri-
cans from an impending threat or preventing a humanitarian catastrophe,
and each also undertaken in part to assist Iraq, at its request, in combating
ISIL.
   Airstrikes Near Erbil and Mount Sinjar. On August 7, 2014, President
Obama announced that he had authorized two military operations in Iraq:
“targeted airstrikes to protect our American personnel, and a humanitarian
effort to help save thousands of Iraqi citizens who are trapped on a moun-
tain without food and water and facing almost certain death.” Office of the
Press Secretary, The White House, Statement by the President (Aug. 7,
2014) (“President Obama August 7 Statement”), https://obamawhitehouse.
archives.gov/the-press-office/2014/08/07/statement-president. In the first
operation, U.S. military forces “conducted targeted airstrikes against
terrorist forces outside the city of Erbil to prevent them from advancing
on the city and to protect our American diplomats and military person-
nel.” Office of the Press Secretary, The White House, Statement by the
President on Iraq (Aug. 9, 2014) (“President Obama August 9 State-
ment”), https://obamawhitehouse.archives.gov/the-press-office/2014/08/
07/statement-president. In the second operation, U.S. forces conducted
airdrops of food and water on Mount Sinjar and targeted airstrikes
against ISIL militants besieging the mountain in order to protect the
stranded Yezidis and assist in their escape. See Office of the Press Secre-
tary, The White House, Statement by the President (Aug. 14, 2014)
(“President Obama August 14 Statement”), https://obamawhitehouse.

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archives.gov/the-press-office/2014/08/14/statement-president; President
Obama August 9 Statement. The President explained:
      When we face a situation like we do on that mountain—with inno-
      cent people facing the prospect of violence on a horrific scale—
      when we have a mandate to help—in this case, a request from the
      Iraqi government—and when we have the unique capabilities to help
      avert a massacre, then I believe the United States of America cannot
      turn a blind eye. We can act, carefully and responsibly, to prevent a
      potential act of genocide.
President Obama August 7 Statement. The President declined to specify a
particular timetable for the airstrikes. See President Obama August 9
Statement. But he also emphasized that the United States was “not going
to have . . . combat troops in Iraq again.” 

 4
   Consistent with the War Powers Resolution, 

(a), Pres-
ident Obama provided a report to Congress less than forty-eight hours
after the operations began:
         As I announced publicly on August 7, 2014, I have authorized the
      U.S. Armed Forces to conduct targeted airstrikes in Iraq. These mili-
      tary operations will be limited in their scope and duration as neces-
      sary to protect American personnel in Iraq by stopping the current
      advance on Erbil by the terrorist group Islamic State of Iraq and the
      Levant and to help forces in Iraq as they fight to break the siege of
      Mount Sinjar and protect the civilians trapped there.
         Pursuant to this authorization, on August 8, 2014, U.S. military
      forces commenced targeted airstrike operations in Iraq.

   4 On August 13, a senior White House official stated that the United States would con-

sider using U.S. ground troops to assist the Iraqi government in evacuating refugees from
Mount Sinjar but reiterated the President’s commitment not to “reintroduc[e] U.S. forces
into combat on the ground in Iraq.” Colin Campbell, White House: We May Use Combat
Troops for Iraq Operation, Bus. Insider, Aug. 13, 2014, https://www.businessinsider.com/
white-house-we-may-use-combat-troops-in-iraq-2014-8; see also 

 (senior official
explaining that any deployment of ground troops to assist in evacuating refuges would be
“different than reintroducing U.S. forces in a combat role to take the fight to ISIL”).
Ultimately, the President determined that ground troops were not necessary because the
humanitarian airdrops and airstrikes had been successful. See President Obama August 14
Statement.

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

        In addition, I have authorized U.S. Armed Forces to provide hu-
     manitarian assistance in Iraq in an operation that commenced on Au-
     gust 7, 2014. These operations will also be limited to supporting the
     civilians trapped on Mount Sinjar.
Office of the Press Secretary, The White House, Letter from the Presi-
dent—War Powers Resolution Regarding Iraq (Aug. 8, 2014) (“August 8
Report to Congress”), https://obamawhitehouse.archives.gov/the-press-
office/2014/08/08/letter-president-war-powers-resolution-regarding-iraq.
The report also explained that, in the President’s judgment, the actions
were “in the national security and foreign policy interests of the United
States.” 

 As authority for the military operations, President Obama
invoked his “constitutional authority to conduct U.S. foreign relations”
and his authority “as Commander in Chief and Chief Executive.” 

   The President and other administration officials emphasized on multi-
ple occasions that both operations were undertaken at the specific re-
quest of the Iraqi government. See, e.g., President Obama August 7
Statement; News Transcript, U.S. Dep’t of Def., Remarks by Secretary
Hagel at a Troop Event, San Diego, California (Aug. 12, 2014), http://
archive.defense.gov/Transcripts/Transcript.aspx?TranscriptID=5485. The
President’s report to Congress likewise indicated that these actions were
“being undertaken in coordination with the Iraqi government.” August 8
Report to Congress.
   Airstrikes Near Mosul Dam. On August 14, the President authorized
further targeted airstrikes against ISIL positions around the Mosul Dam
to assist the Iraqi forces in recapturing and establishing control of the
dam. See Office of the Press Secretary, The White House, Letter from
the President—War Powers Resolution Regarding Iraq (Aug. 17, 2014)
(“August 17 Report to Congress”), https://obamawhitehouse.archives.
gov/the-press-office/2014/08/17/letter-president-war-powers-resolution-
regarding-iraq. In a report to Congress describing his authorization of
this third set of airstrikes, the President cited the dangers posed by ISIL’s
control of the dam:
     On August 14, 2014, I authorized the U.S. Armed Forces to conduct
     targeted air strikes to support operations by Iraqi forces to recapture
     the Mosul Dam. These military operations will be limited in their
     scope and duration as necessary to support the Iraqi forces in their

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     efforts to retake and establish control of this critical infrastructure
     site, as part of their ongoing campaign against the terrorist group the
     Islamic State of Iraq and the Levant (ISIL). The failure of the Mosul
     Dam could threaten the lives of large numbers of civilians, endanger
     U.S. personnel and facilities, including the U.S. Embassy in Bagh-
     dad, and prevent the Iraqi government from providing critical ser-
     vices to the Iraqi populace.

 Administration officials noted that the airstrikes against ISIL positions
in and around the Mosul Dam, like the prior sets of strikes, were under-
taken “at the request of the Iraqi government.” U.S. Dep’t of Def., News
Release, No. NR-432-14, Statement from Pentagon Press Secretary Rear
Admiral John Kirby (Aug. 18, 2014), http://archive.defense.gov/Releases/
Release.aspx?ReleaseID=16891. The strikes began on August 15 and ul-
timately assisted Iraqi forces in regaining control of the dam. See 

   Airstrikes Near Amirli. By late August, it had become clear that a hu-
manitarian crisis was developing in Amirli, a town in northern Iraq
populated by Shiite Turkmen that had been besieged by ISIL militants for
many weeks. See, e.g., Ben Hubbard, Dozens Killed at Sunni Mosque in
Iraq After Attack on Shiite Leader, N.Y. Times Int’l, Aug. 22, 2014, at
A6. The siege had left the community without sufficient food, water, or
medical supplies, and Iraqi leaders and human rights officials were
appealing to the international community for assistance. See 

 Further,
because ISIL viewed the Shiite residents of the town as “infidels,” the
members of the community faced possible mass executions if ISIL
gained control of the town. See id.; see also State Department June 15
Press Statement (noting ISIL’s claim that it had massacred 1700 Iraqi
Shiite air force recruits). In light of these developments, the State De-
partment indicated that the United States was “very concerned about the
dire conditions for the mainly Turkmen population in Amirli.” Office of
Press Relations, U.S. Dep’t of State, Daily Press Briefing (Aug. 28,
2014) (“State Department August 28 Daily Press Briefing”), https://2009-
2017.state.gov/r/pa/prs/dpb/2014/08/231125.htm. This concern was also
reflected in earlier calls by U.N. officials for “immediate action to pre-
vent the possible massacre of [Amirli’s] citizens” and to address the
“desperate” situation and “inhuman conditions” there. UN News, Iraq:
UN Envoy Calls for Immediate Action to Avert Possible “Massacre” in

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

Northern Town (Aug. 23, 2014), https://news.un.org/en/story/2014/08/
475762-iraq-un-envoy-calls-immediate-action-avert-possible-massacre-
northern-town; see also Office of the High Commissioner, U.N. Human
Rights, Iraqi Civilians Suffering “Horrific” Widespread and Systematic
Persecution—Pillay (Aug. 25, 2014) (noting the “possible imminent
massacre” of the 13,000 members of the Amirli Turkmen community and
calling upon the “Government of Iraq and the Kurdistan region of Iraq,
and the international community” to “take all necessary measures . . . to
protect members of ethnic and religious communities”), https://www.
ohchr.org/EN/NewsEvents/Pages/DisplayNews.aspx?NewsID=14961&
LangID=E.
   On August 28, in response to this unfolding humanitarian crisis, Pres-
ident Obama authorized airdrops of supplies to Amirli as well as “tar-
geted airstrikes in support of [the humanitarian] operation.” Office of
the Press Secretary, The White House, Letter from the President—War
Powers Resolution Regarding Iraq (Sept. 1, 2014) (“September 1 Report
to Congress”), https://obamawhitehouse.archives.gov/the-press-office/
2014/09/01/letter-president-war-powers-resolution-regarding-iraq. U.S.
aircraft dropped 109 bundles of humanitarian aid by August 31, and
additional aid was delivered by coordinated British, French, and Aus-
tralian airdrops. See News Release, U.S. Central Command, Release No.
20140835, U.S. Military Conducts Airstrikes Against ISIL, Airdrops
Humanitarian Aid Near Amirli (Aug. 30, 2014) (“CENTCOM August 30
Release”), http://www.centcom.mil/MEDIA/NEWS-ARTICLES/News-
Article-View/Article/884834/us-military-conducts-airstrikes-against-isil-
airdrops-humanitarian-aid-near-ami. U.S. aircraft also conducted strikes
on ISIL positions in support of the humanitarian operation. 

   Within forty-eight hours after the Amirli operation began, President
Obama reported the operation to Congress:
     On August 28, 2014, I . . . authorized U.S. Armed Forces to conduct
     targeted airstrikes in support of an operation to deliver humanitarian
     assistance to civilians in the town of Amirli, Iraq, which is surround-
     ed and besieged by ISIL. Pursuant to this authorization, on August
     30, 2014, U.S. military forces commenced targeted airstrike opera-
     tions in the vicinity of Amirli, Iraq. These additional operations will
     be limited in their scope and duration as necessary to address this

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     emerging humanitarian crisis and protect the civilians trapped in
     Amirli.
September 1 Report to Congress. The President indicated that the Amirli
operation, like the previous operations, had been “undertaken in coord-
ination with and at request of the Iraqi government.” Id.; see also CENT-
COM August 30 Release (noting the actions were taken “[a]t the request
of the Government of Iraq”).
   Airstrikes Near Haditha Dam. Throughout August, ISF and allied trib-
al fighters maintained control of the Haditha Dam against advances by
ISIL militants. See Jihadists Rout Kurds, N.Y. Times, Aug. 8, 2014, at
A1; Helene Cooper et al., U.S. Intervention in Iraq Extends to a Second
Dam, N.Y. Times, Sept. 8, 2014, at A8. On September 6, 2014, to support
these efforts, President Obama authorized the U.S. military to launch
airstrikes against ISIL positions around the dam. See Office of the Press
Secretary, The White House, Letter from the President—War Powers
Resolution Regarding Iraq (Sept. 8, 2014) (“September 8 Report to Con-
gress”), https://obamawhitehouse.archives.gov/the-press-office/2014/09/
08/letter-president-war-powers-resolution-regarding-iraq. These airstrikes
were conducted “in support of Iraqi Security Forces’ efforts to retain
control” of the dam, because the “destruction of the dam or release of
water would create a level of flooding that would potentially pose a cata-
strophic threat to thousands of Iraqis along the Euphrates valley from
Anbar province into parts of Baghdad, including possible flooding in
areas in and around the Baghdad International Airport, where hundreds of
U.S. personnel reside.” Office of the Press Secretary, The White House,
Statement by NSC Spokesperson Caitlin Hayden on Airstrikes Around the
Haditha Dam (Sept. 7, 2014) (“NSC September 7 Statement”), https://
obamawhitehouse.archives.gov/the-press-office/2014/09/07/statement-
nsc-spokesperson-caitlin-hayden-airstrikes-around-haditha-dam; see also
News Release, U.S. Dep’t of Defense, Release No. NR-468-14, Statement
from Pentagon Press Secretary Rear Admiral John Kirby on Haditha Dam
Airstrikes (Sept. 7, 2014), http://archive.defense.gov/Releases/Release.
aspx?ReleaseID=16927 (noting that flooding that might have resulted
from a catastrophic failure of the dam “would have threatened U.S. per-
sonnel and facilities in and around Baghdad, as well as thousands of Iraqi


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          Targeted Airstrikes Against the Islamic State of Iraq and the Levant

citizens”). President Obama reported this operation to Congress within
forty-eight hours:
       On September 6, 2014, pursuant to my authorization, U.S. Armed
       Forces commenced targeted airstrikes in the vicinity of the Haditha
       Dam in support of Iraqi forces in their efforts to retain control of and
       defend this critical infrastructure site from ISIL. These additional
       military operations will be limited in their scope and duration as
       necessary to address this threat and prevent endangerment of U.S.
       personnel and facilities and large numbers of Iraqi civilians.
September 8 Report to Congress. President Obama again emphasized
that, as in prior operations, he had authorized the use of force “in coordi-
nation with and at the request of the Iraqi government.” Id.; see also U.S.
Dep’t of Def., News Transcript, Joint Press Availability by Secretary
Hagel and Minister Alasania in Georgia (Sept. 7, 2014), http://archive.
defense.gov/Transcripts/Transcript.aspx?TranscriptID=5499 (noting that
the “Iraqi security forces on the ground . . . conceived of the operation”
and the “Iraqi government asked [the United States] for [its] support in
th[e] strikes”). 5

                                           II.

  In our recent opinion concerning the President’s authority to conduct
military operations in Libya, we explained in detail our framework for
analyzing the President’s legal authority to use military force abroad
without prior congressional authorization. See Authority to Use Military
Force in Libya, 

, 27–33 (2011) (“Military Force in
Libya”). In light of that discussion, we need not provide a detailed expla-
nation of our framework here. Instead, we will summarize briefly the


   5 Although the President had begun developing his new comprehensive strategy to
counter ISIL at the time that he authorized airstrikes around the Haditha Dam, see supra
note 1, it is our understanding that those airstrikes were not intended to implement the
new strategy, which had not yet been finalized or announced when the strikes were
initiated. Rather, as the President’s Report to Congress explains, the Haditha airstrikes
were an independent operation “limited in their scope and duration” as necessary to
protect the dam, U.S. personnel and facilities, and Iraqi civilians. September 8 Report to
Congress.

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relevant legal principles before applying them to the airstrike operations
described above.
   As our Libya opinion explains, Attorneys General and this Office have
consistently concluded that “‘the President has the power to commit
United States troops abroad,’ as well as to ‘take military action,’ ‘for the
purpose of protecting important national interests,’ even without specific
prior authorization from Congress.” 

 at 27–28 (quoting Authority to
Use United States Military Forces in Somalia, 

, 9 (1992)
(“Military Forces in Somalia”)). This power is rooted in the President’s
constitutional authority as Chief Executive and Commander in Chief of
the armed forces. U.S. Const. art. II, § 1, cl. 1; id. § 2, cl. 1. The assign-
ment of the “executive Power” to the President has, over time, been
understood to give him the “‘vast share of responsibility for the conduct
of our foreign relations,’” Am. Ins. Ass’n v. Garamendi, 

(2003) (quoting Youngstown Sheet & Tube Co. v. Sawyer, 

,
610 –11 (1952) (Frankfurter, J., concurring)), as well as “independent
authority ‘in the areas of foreign policy and national security,’” 

 at 429
(quoting Haig v. Agee, 

 (1981)). And the President’s
authority as Commander in Chief gives him the authority to superintend
and direct the movements of the military forces placed at his command.
See Loving v. United States, 

 (1996); Fleming v. Page,

 (1850). The President also holds an “implicit
advantage . . . over the legislature under our constitutional scheme in sit-
uations calling for immediate action,” because of his ability to act and
respond to developing situations with greater facility and speed. Presi-
dential Power to Use the Armed Forces Abroad Without Statutory Author-
ization, 4A Op. O.L.C. 185, 187 (1980) (“Presidential Power”); see also
Presidential Authority to Permit Incursion Into Communist Sanctuaries in
the Cambodia-Vietnam Border Area, 1 Op. O.L.C. Supp. 313, 314 (1970)
(noting that the Framers “recognized the need for quick executive re-
sponse to rapidly developing international situations”).
   Presidents have exercised these authorities numerous times throughout
the Nation’s history to deploy the armed forces abroad without either a
declaration of war or other congressional authorization, beginning in the
earliest days of the Republic. See Military Forces in Somalia, 16 Op.
O.L.C. at 9 (citing an example from 1801); Presidential Power, 4A Op.
O.L.C. at 187 (“Our history is replete with instances of presidential uses
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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

of military force abroad in the absence of prior congressional approval.”).
See generally Barbara Salazar Torreon, Cong. Research Serv., R42738,
Instances of Use of United States Armed Forces Abroad, 1798–2013, at
2–33 (Aug. 30, 2013) (“Instances of Force Abroad ”) (citing numerous
examples). In the foreign affairs and national security context, where
judicial review is rare, see Agee, 

, such a “pattern of
executive conduct, made under claim of right, extended over many dec-
ades[,] and engaged in by Presidents of both parties, evidences the exist-
ence of broad constitutional power.” Military Force in Libya, 35 Op.
O.L.C. at 29–30 (internal quotation marks omitted); see also Proposed
Deployment of United States Armed Forces into Bosnia, 

, 330–31 (1995) (“Proposed Bosnia Deployment ”) (noting that the
“scope and limits” of the President’s and Congress’s respective powers
have been “clarified by 200 years of practice”).
   To be sure, the Constitution also gives Congress the power to “declare
War,” to provide for the common defense, and to raise, support, maintain,
and make rules for the armed forces. U.S. Const. art. I, § 8, cls. 1, 11–14.
These congressional powers may limit the President’s authority to initiate
without prior congressional authorization a “prolonged and substantial”
“planned military engagement that constitutes a ‘war’ within the meaning
of the Declaration of War Clause.” Military Force in Libya, 35 Op.
O.L.C. at 31. They may also permit Congress in certain respects to restrict
how the President exercises his military authorities. See id. at 28. But “the
historical practice of presidential military action without congressional
approval precludes any suggestion that Congress’s authority to declare
war covers every military engagement, however limited, that the President
initiates.” Id. at 31. Indeed, “Congress itself has implicitly recognized”
the President’s unilateral authority to initiate military engagements in the
War Powers Resolution, which, by imposing reporting and other require-
ments on the President’s introduction of armed forces into hostilities or
imminent hostilities absent a congressional declaration of war, “‘recog-
nizes and presupposes the existence of unilateral presidential authority to
deploy armed forces’” into such situations. Id. at 30 (quoting Deployment
of United States Armed Forces into Haiti, 

, 175 (1994)
(“1994 Haiti Deployment ”)).
   Synthesizing these precedents in our Libya opinion, we explained that,
in any particular instance, the President’s authority to order military
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action abroad without prior congressional approval turns on two consider-
ations: first, whether the contemplated action would serve “sufficiently
important national interests” to “permit the President’s action as Com-
mander in Chief and Chief Executive”; and second, whether the contem-
plated action would be sufficiently limited in “nature, scope, and dura-
tion” so as not to constitute a “war” requiring prior congressional approv-
al under the Declaration of War Clause. 

. We now turn to an
analysis of the airstrike operations detailed above under this two-part
framework.

                                     A.

  We consider first whether the operations served “sufficiently important
national interests” to fall within the President’s constitutional authority as
Commander in Chief and Chief Executive. Military Force in Libya, 35
Op. O.L.C. at 33. In authorizing the targeted airstrikes against ISIL,
President Obama identified at least three relevant national interests:
protecting American lives and property; assisting an ally or strategic
partner at its request; and protecting endangered populations against
humanitarian atrocities, including possible genocide. In our view, a
combination of these interests supported the President’s constitutional
authority as Commander in Chief to order each of the airstrike operations
described above without express congressional authorization.

                                     1.

   The first national interest identified by President Obama—the protec-
tion of American citizens and property—has long been recognized as a
basis on which Presidents may authorize military action abroad without
prior congressional approval. See Presidential Power, 4A Op. O.L.C. at
121 (“It is well established that the President has the constitutional power
as Chief Executive and Commander-in-Chief to protect the lives and
property of Americans abroad.”); Military Forces in Somalia, 16 Op.
O.L.C. at 9 (“At the core of ” the President’s power to use military force
without prior congressional authorization “is the President’s authority to
take military action to protect American citizens, property, and interests
from foreign threats.”); see also United States v. Verdugo-Urquidez, 

 (1990) (noting that “[t]he United States frequently employs

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

Armed Forces outside this country . . . for the protection of American
citizens”); In re Neagle, 

, 63–64 (1890) (recognizing that the
obligation to protect American citizens abroad is among the President’s
“rights, duties, and obligations growing out of the Constitution itself ”);
Durand v. Hollins, 

 (C.C.S.D.N.Y. 1860) (No. 4186)
(stating that “the interposition of the president abroad, for the protection
of the citizen, must necessarily rest in his discretion”). Presidents have
relied on this interest numerous times to support both defensive and
offensive military action abroad. See, e.g., J. Reuben Clark, U.S. Solicitor,
Dep’t of State, Right to Protect Citizens in Foreign Countries by Landing
Forces 34–38 (3d rev. ed. 1933) (“Right to Protect ”) (collecting examples
prior to 1910); Authority of the President to Repel the Attack in Korea, 23
Dep’t of State Bull. 173, 177–78, reprinted in H.R. Rep. No. 81-2495, at
61, 67–68 (1950) (collecting examples between 1812 and 1932) (“Korea
Memorandum”); Instances of Force Abroad at 2–33 (citing additional
examples). President McKinley, for instance, dispatched 5,000 troops to
China in significant part to protect American lives and property during the
Boxer Rebellion. See William McKinley, Annual Message of the Presi-
dent to Congress (Dec. 3, 1900), Papers Relating to the Foreign Relations
of the United States, 1900, at XI–XIV (1902) (describing the operation in
detail); see also Deployment of United States Armed Forces to Haiti, 

, 32 (2004) (“2004 Haiti Deployment ”). President Taft sent
more than 2,000 troops to Nicaragua in 1912 in part to protect Americans
during an ongoing revolution in that country. Right to Protect at 119–22;
see also W.H. Taft, Annual Message of the President to Congress (Dec. 3,
1912), Papers Relating to the Foreign Relations of the United States,
1912, at XII–XIII (1919). And President Johnson ordered military inter-
vention in the Dominican Republic in 1965 in large part to protect Ameri-
cans living there. See 2004 Haiti Deployment, 28 Op. O.L.C. at 32. More
recently, in 2004, President George W. Bush deployed troops to Haiti in
part to protect the thousands of Americans living there who “would [have
been] in danger if the country [had] descend[ed] into lawlessness.” Id.
   In our view, it was reasonable for the President to rely on a national
interest in protecting American personnel and property in authorizing the
airstrikes around Erbil, the Mosul Dam, and the Haditha Dam. As noted
earlier, numerous American military advisers, diplomats, and other civil-
ians are based in Erbil. Given ISIL’s brutal treatment of the populations it

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encounters and those who oppose its aims, see supra Part I, the lives of
these Americans would have been placed in jeopardy if ISIL had taken
control of Erbil. The airstrikes against ISIL forces outside the city were
therefore justified in order to protect these American lives. Similarly,
American lives and property in Baghdad would have been placed in
jeopardy if ISIL had destroyed the Mosul Dam—whether through pur-
poseful action or an inability to perform the “extraordinary engineering
measures” necessary to maintain it, Geologic Setting of Mosul Dam at 2—
or if ISIL had taken control of and destroyed or released floodwaters from
the Haditha Dam, see NSC September 7 Statement. More than 5,000
contractors, including 2,000 U.S. citizens, were working at the U.S.
Embassy in Baghdad as of June. See Dan Lamothe, Diplomats, Pilots, and
Hired Guns: Here Are the Americans Left in Iraq, Wash. Post, June 12,
2014, https://www.washingtonpost.com/news/checkpoint/wp/2014/06/12/
diplomats-pilots-and-hired-guns-here-are-the-americans-left-in-iraq.
The destruction of the Mosul Dam could have resulted in flooding in
Baghdad, see Mosul Dam Letter, which the President determined could
have “endanger[ed] U.S. personnel and facilities, including the U.S.
Embassy in Baghdad, and prevent[ed] the Iraqi government from provid-
ing critical services” to the populace. August 17 Report to Congress. The
destruction of the Haditha Dam could similarly have caused flooding in
the southern areas of Baghdad, including areas where U.S. personnel are
located, which the President determined could have “endanger[ed] U.S.
personnel and facilities.” September 8 Report to Congress; see also NSC
September 7 Statement. In light of these risks, it was also reasonable for
the President to rely on the national interest in protecting U.S. personnel
and property in authorizing military action to help Iraqi forces retake the
Mosul Dam and retain control of the Haditha Dam.

                                     2.

   In authorizing the airstrike operations at issue in this opinion, President
Obama also invoked a national interest in assisting Iraq, a strategic part-
ner, in its campaign against ISIL. See August 8 Report to Congress (indi-
cating the airstrikes near Erbil and Mount Sinjar would “help forces in
Iraq” and were “undertaken in coordination with the Iraqi government”);
August 17 Report to Congress (indicating the airstrikes around the Mosul

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         Targeted Airstrikes Against the Islamic State of Iraq and the Levant

Dam were undertaken “to support the Iraqi forces in their efforts” to
recapture the dam and in “their ongoing campaign against [ISIL]”); Sep-
tember 1 Report to Congress (noting the operation had been undertaken
“in coordination with and at the request of the Iraqi government”); Sep-
tember 8 Report to Congress (indicating the airstrikes around Haditha
Dam were undertaken “in support of Iraqi forces in their efforts to retain
control of and defend this critical infrastructure site from ISIL”). We
believe that it was reasonable for the President to rely on this interest, in
combination with a national interest in protecting American citizens and
property or averting a humanitarian catastrophe, in ordering the use of
military force abroad.
   Our Office has previously recognized that, in authorizing military ac-
tion abroad, the President may rely on a national interest in assisting an
ally or strategic partner at its request. In our 1980 opinion on possible
uses of force related to the Iranian hostage crisis, for example, we identi-
fied “defending our allies” as a purpose for which the President may
constitutionally use force without prior congressional approval, and
pointed to the deployment of troops to Korea as “precedent . . . for the
commitment of United States armed forces, without prior congressional
approval or declaration of war, to aid an ally in repelling an armed
invasion.” Presidential Power, 4A Op. O.L.C. at 186 n.2, 187–88. 6
Similarly, in our 1994 opinion concluding that the President had constitu-
tional authority to send 20,000 troops to Haiti to forcibly remove its
military dictators from power, we relied in significant part on the fact that
the planned deployment was to take place at the invitation of Haiti’s
legitimate government, citing in support several prior examples of Presi-
dents deploying the military abroad at the request of foreign countries.

   6 The fact that this national interest supported the Korea operation does not mean that

the Korea deployment was sufficiently limited in nature, scope, and duration to be within
the President’s constitutional authority to act without congressional authorization. See
1994 Haiti Deployment, 18 Op. O.L.C. at 178–79. We take no position on the latter
question in this opinion. See The President and the War Power: South Vietnam and the
Cambodian Sanctuaries, 1 Op. O.L.C. Supp. 321, 329 (1970) (noting that President
Truman’s action in Korea had ignited a “Great Debate” in Congress over the President’s
war power); Proposed Bosnia Deployment, 19 Op. O.L.C. at 331–32 n.5 (noting that
“[t]he boldest claim of Executive authority to wage war without congressional authoriza-
tion was made at the time of the Korean War,” and that “[s]uch sweeping claims of
inherent Executive authority have been sharply criticized”).

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1994 Haiti Deployment, 18 Op. O.L.C. at 174 n.1, 178–79 & n.10 7; see
also Leonard C. Meeker, Legal Adviser, Dep’t of State, The Legality of

   7  The discussion of U.S. military action taken at the request of foreign governments in
our 1994 Haiti opinion appeared in the context of a discussion of the Declaration of War
Clause, rather than a discussion of national interests supporting an exercise of the Com-
mander in Chief power. But that is because the entire constitutional discussion in that
opinion was framed as a discussion of the Declaration of War Clause. This feature of the
opinion is not unusual: the two-part inquiry we developed in our Libya opinion is a recent
refinement in this Office’s jurisprudence, and our earlier opinions frequently analyzed the
question of the President’s constitutional authority to deploy the military abroad without
prior congressional authorization under the rubric of a single inquiry, asking either
whether a contemplated military action fell within the President’s constitutional power as
Commander in Chief and Chief Executive to act in the national interest, see, e.g., 2004
Haiti Deployment, 28 Op. O.L.C. at 31–33; Military Forces in Somalia, 16 Op. O.L.C. at
9–12; Presidential Power, 4A Op. O.L.C. at 186–88, or whether a proposed use of force
would constitute a “war” within the meaning of the Constitution, see, e.g., Proposed
Bosnia Deployment, 19 Op. O.L.C. at 330–34; 1994 Haiti Deployment, 18 Op. O.L.C. at
177–79. The analysis in these earlier opinions, however, frequently incorporated in
substance both components of the two-part framework set forth above.
     Thus, even though we considered assistance to an ally or partner in our 1994 Haiti
opinion in the context of a discussion of the Declaration of War Clause, our opinion
appeared to invoke that interest at least in part as a justification for the use of force
abroad, not simply as an explanation for why the conflict was likely to be limited in
nature, scope, and duration. In introducing historical examples of such assistance, for
example, we observed that “the President, as Chief Executive and Commander in Chief
. . . may, absent specific legislative restriction, deploy United States armed forces abroad
or to any particular region,” and then noted that “Presidents have often utilized this
authority, in the absence of specific legislative authorization, to deploy United States
military personnel into foreign countries at the invitation of the legitimate governments of
those countries.” 1994 Haiti Deployment, 18 Op. O.L.C. at 178 (internal quotation marks
omitted). This formulation suggests that we recognized that prior Presidents had consid-
ered a foreign government’s request for assistance to be an overall justification for the
deployment of troops abroad under their Chief Executive and Commander in Chief
authority, not simply an indicator of a conflict’s likely scope. The examples of prior
presidential action we cited in our opinion are consistent with this characterization. See
infra pp. 103 –109 (discussing examples of Nicaragua, Greenland, Iceland, and the
Philippines also cited in 1994 Haiti opinion). Further—and significantly—our 1994 Haiti
opinion also recognized that the mere fact that the United States “deploys its troops into a
country at the invitation of that country’s legitimate government” does not mean that the
engagement is not a “war,” and conducted a separate analysis of the proposed Haitian
deployment’s “nature, scope, and duration” to establish that it did not “rise to the level of
‘war.’” 1994 Haiti Deployment, 18 Op. O.L.C. at 178–79. These features of our 1994
opinion suggest that its discussion of assistance to an ally or partner fits most naturally
into the “national interest” element of our current two-part test.

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          Targeted Airstrikes Against the Islamic State of Iraq and the Levant

United States Participation in the Defense of Viet-Nam, 54 Dep’t of State
Bull. 474, 489 (1966) (“Participation in Viet-Nam”) (concluding that the
President had constitutional “authority to commit United States forces in
the collective defense of South Viet-Nam” on the request of that country
and that “[t]his authority stems from the constitutional powers of the
President”).
   Historical practice is consistent with this position. Presidents have tak-
en military action abroad or deployed U.S. military personnel into for-
eign countries without prior congressional approval on numerous occa-
sions for the purpose of assisting an ally or partner at its request. In
February 1874, for example, rioting began in still-independent Hawaii
after the election of a new king. Right to Protect at 67. “[A]t the earnest
solicitation of [Hawaii’s] government,” U.S. troops landed amid active
rioting in Honolulu “to aid in restoring order.” Id. (quoting Report of the
Secretary of the Navy, H.R. Exec. Doc. No. 43-1, pt. 3, at 8 (1874)); see
also Instances of Force Abroad at 6. In 1912, an attempted coup resulted
in “open rebellion” against the government in Nicaragua. Papers Relat-
ing to the Foreign Relations of the United States, 1912, at 1032. In re-
sponse, the Government of Nicaragua requested that the United States
“guarantee with its forces security for the property of American citizens”
and provide “protection to all inhabitants of the Republic.” Id.; see also
Right to Protect at 119–20. Conveying this request to President Taft, the
Secretary of State asked for the deployment of troops to Nicaragua “in
view of the specific request of the Nicaraguan Government and of the
seemingly possible danger of resultant anarchy.” Papers Relating to the
Foreign Relations of the United States, 1912, at 1032–33. President Taft
granted the request. See id. at 1033. And in 1919, at the request of Italian


    We do not mean to imply that if the government of a particular territory requests that
the United States use armed force in that territory, such a request cannot also be relevant
in some circumstances to whether an action constitutes a “war.” In our opinion regarding
a proposed deployment to Bosnia, for instance, we explained that the “consensual nature”
of the operation—the fact that the parties who controlled the territory at issue had re-
quested intervention—tended to suggest that “little or no resistance to the deployment
w[ould] occur,” and served to distinguish the deployment of force from traditional wars
aimed at conquest or occupation of territory, both considerations that inform an analysis
of the anticipated “nature, scope, and duration” of a conflict. Proposed Bosnia Deploy-
ment, 19 Op. O.L.C. at 332.

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authorities and without the prior knowledge or consent of Congress, U.S.
troops landed at Trau, Dalmatia—territory that was the subject of a post-
World War I dispute between Italian and Serbian forces—in order to
prevent an imminent conflict. See Instances of Force Abroad at 9; Clar-
ence Arthur Berdahl, War Powers of the Executive in the United States
56 (1921). In response to a Senate resolution seeking information about
the incident, the Secretary of the Navy emphasized the “fact that Italian
authorit[ies] [had] requested [the] action” and that, had the United States
not acted, “a state of actual war” might have resulted. Landing Marines
at Trau, Dalmatia, S. Doc. No. 66-117, at 2 (1919). 8
   Similarly, before the United States joined the Second World War—but
after the war had begun in Europe and it was feared that Germany might
attack the Western Hemisphere—President Franklin D. Roosevelt unilat-
erally authorized military action “designed to aid the allied forces” at the
request of foreign officials. The President and the War Power: South
Vietnam and the Cambodian Sanctuaries, 1 Op. O.L.C. Supp. 321, 330
(1970). Pursuant to an agreement made with a Danish minister, President
Roosevelt ordered the U.S. military to occupy Greenland after Denmark
fell to Germany in 1940. Id.; see also 1994 Haiti Deployment, 18 Op.
O.L.C. at 178. And in 1941, he authorized U.S. troops to occupy Iceland
“in defense of that country,” pursuant to an agreement he concluded with
Iceland’s Prime Minister. Korea Memorandum, 23 Dep’t of State Bull. at
175, reprinted in H.R. Rep. No. 81-2495, at 65; see also 1994 Haiti
Deployment, 18 Op. O.L.C. at 178. Although these actions plainly fur-
thered the national security interest in preventing Germany from gaining a
foothold in the Western Hemisphere and attacking transatlantic shipping
lanes, President Roosevelt indicated that the actions were also undertaken
to assist friendly nations in defending their territory against Germany’s
aggression. See Samuel I. Rosenman, The Public Papers and Addresses of

   8In congressional debates about the Trau incident, one Senator argued that the de-
ployment of U.S. forces had been authorized by the “practically unlimited resources and
unlimited power” Congress had given the President to fight World War I. 58 Cong. Rec.
6124–25 (1919). But as other Senators pointed out, at the time the troops were sent to
Dalmatia, the United States had already signed an armistice, and in any event had never
been at war with Italy or Serbia. See id. at 6123–29; see also Landing at Trau Hotly
Condemned in Senate Debate, N.Y. Times, Sept. 30, 1919 (describing the competing
views).

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Franklin D. Roosevelt 1941, at 262 (“[T]he Government of the United
States, while undertaking this defensive measure for the preservation of
the independence and security of the democracies of the New World,
[will] at the same time be afforded the privilege of cooperating in this
manner with your Government in the defense of this historic democracy
of Iceland.” (quoting message sent by President Roosevelt to the Prime
Minister of Iceland)); id. at 96–97 (quoting President Roosevelt’s an-
nouncement that the establishment of U.S. bases in Greenland was “new
proof of our continuing friendliness to Denmark”).
   Several years later, in July of 1958, President Eisenhower sent a “con-
tingent of United States Marines” to Lebanon in response to an “urgent
request” from its president for assistance in the face of a “violent insur-
rection” whose “avowed purpose” was to “overthrow the legally consti-
tuted government of Lebanon.” Special Message to the Congress on the
Sending of United States Forces to Lebanon (July 15, 1958), Pub. Papers
of Pres. Dwight D. Eisenhower 550, 550–51 (1958). President Eisen-
hower explained to Congress that “United States forces are being sent to
Lebanon to protect American lives and by their presence to assist the
Government of Lebanon in the preservation of Lebanon’s territorial
integrity and independence.” Id.; see also Statement by the President on
the Lebanese Government’s Appeal for U.S. Forces (July 15, 1958),
Pub. Papers of Pres. Dwight D. Eisenhower 549, 549–50 (1958). “As we
act at the request of a friendly government to help it preserve its inde-
pendence and to preserve law and order which will protect American
lives,” the President added, “we are acting to reaffirm and strengthen
principles upon which the safety and security of the United States de-
pend.” Special Message to Congress on Lebanon, Pub. Papers of Pres.
Dwight D. Eisenhower at 552 (1958). Vice President Nixon made clear
that the “President had the constitutional power to do what he did” in
part because of the U.S. interest in “strengthen[ing] th[e] [Lebanese]
government in its efforts to resist forces in its country which were
stimulated and materially assisted by forces outside the country.” 104
Cong. Rec. 14,548 (1958). The Vice President explained that the “fail-
ure to come to the aid of a government that had been friendly to the
United States” and had requested America’s help “would have struck
fear and consternation and probably panic into the hearts of the friends


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of the United States not only in that area, but all the way from Morocco
on the Atlantic clear over to the Pacific area.” 

. 9
   In 1982, President Reagan again sent U.S. troops to Lebanon “[i]n re-
sponse to the formal request of the Government of Lebanon,” this time to
help ensure the departure of Palestine Liberation Organization leadership,
offices, and combatants from Beirut and the restoration of Lebanese
government authority in the area. Letter to the Speaker of the House and
the President Pro Tempore of the Senate on the Deployment of United
States Forces in Beirut, Lebanon (Aug. 24, 1982), 2 Pub. Papers of Pres.
Ronald Reagan 1078, 1078 (1982). See generally The Situation in the
Middle East: Hearing Before the S. Comm. on Foreign Relations, 97th
Cong. 1–14 (1982). In a notification to Congress “consistent with the War
Powers Resolution,” President Reagan stated that U.S. forces had been
deployed, “pursuant to the President’s constitutional authority with re-
spect to the conduct of foreign relations and as Commander-in-Chief of
the United States Armed Forces,” to “assist the Government of Lebanon
in carrying out its responsibilities concerning the withdrawal [from Bei-
rut] of . . . personnel [associated with the Palestine Liberation Organiza-
tion] under safe and orderly conditions,” as agreed to by the Government
of Lebanon, the Government of Israel, and the Palestine Liberation Or-

    9 In 1957, Congress had passed a Joint Resolution to Promote Peace and Stability in

the Middle East, which gave the President the authority to “use armed forces to assist”
nations or groups of nations in the Middle East if they “request[ed] assistance against
armed aggression from any country controlled by international communism.” 

, 

, 5 (1957). After President Eisenhower deployed troops to Lebanon,
there was some discussion in Congress about whether the deployment fit within the terms
of this resolution, with several Senators expressing the position that it did not. See Arthur
Krock, Law and Intervention: An Analysis of Eisenhower Doctrine’s Application to U.S.
Landing in Lebanon, N.Y. Times, July 16, 1958, at 8; see also Jane E. Stromseth, Under-
standing Constitutional War Powers Today: Why Methodology Matters, 

, 870 n.132 (1996) (noting the debate on the question). In any event, Vice President
Nixon subsequently made clear that the President had acted solely in reliance on his
constitutional authority, see 104 Cong. Rec. 14,548 (1958), and later Executive Branch
opinions have described President Eisenhower’s deployment of troops to Lebanon as
having been undertaken without statutory authorization, see, e.g., Participation in Viet-
Nam, 54 Dep’t of State Bull. at 484–85; Memorandum for President Lyndon Johnson
from Secretary of State Dean Rusk, Re: Legal Basis for Sending American Forces to Viet-
Nam (June 29, 1964), reprinted in Stephen M. Griffin, A Bibliography of Executive
Branch War Powers Opinions Since 1950, 

, 658–61 (2013).

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         Targeted Airstrikes Against the Islamic State of Iraq and the Levant

ganization. Letter on the Deployment of United States Forces in Beirut,
Lebanon, 2 Pub. Papers of Pres. Ronald Reagan at 1078–79 (1982). And
in his remarks to the Nation on the deployment, the President emphasized
the “irreversible commitment” of the United States “to the survival and
territorial integrity of friendly states.” Address to the Nation on United
States Policy for Peace in the Middle East (Sept. 1, 1982), 2 Pub. Papers
of Pres. Ronald Reagan 1093, 1093 (1982). 10
   The next year, when Grenada experienced widespread anarchy and vi-
olence after a “Revolutionary Military Council” assassinated the Prime
Minister and several other government officials and seized political
power, President Reagan authorized the deployment of nearly 2,000 U.S.
troops to invade the island, supported by the U.S. Air Force and Navy.
See Conyers v. Reagan, 

, 1125–26 (D.C. Cir. 1985); Rich-
ard F. Grimmet, Cong. Research Serv., R42699, The War Powers Resolu-
tion: After Thirty-Eight Years 15 (Sept. 24, 2012) (“War Powers Resolu-
tion”). The President noted in oral remarks that he had “received an
urgent, formal request” from the Organization of Eastern Caribbean
States (“OECS”), of which Grenada was a member, “to assist in a joint
effort to restore order and democracy on the island of Grenada.” Remarks
of the President and Prime Minister Eugenia Charles of Dominica An-
nouncing the Deployment of United States Forces in Grenada (Oct. 25,
1983), 2 Pub. Papers of Pres. Ronald 

 (1983). 11 Presi-


   10 The U.S. troops formed part of a multinational force that was sent to the country on

multiple occasions beginning in August 1982 to “facilitate the restoration of Lebanese
Government sovereignty and authority” and “thereby further the efforts of the Govern-
ment of Lebanon to assure the safety of persons in the area and bring to an end the
violence” in the region. Letter to the Speaker of the House and President Pro Tempore of
the Senate Reporting on United States Participation in the Multinational Force in Leba-
non (Sept. 29, 1982), 2 Pub. Papers of Pres. Ronald 

 (1982). Although
President Reagan indicated repeatedly that the troops would not engage in hostilities
except in self-defense, the ongoing hostilities in the country resulted in the deaths of
numerous U.S. troops, and President Reagan ultimately received legislative authorization
for continuing the operations beyond October 1983. See Richard F. Grimmet, Cong.
Research Serv., R42699, The War Powers Resolution: After Thirty-Eight Years 13–15
(Sept. 24, 2012); Multinational Force in Lebanon Resolution, 

 Stat.
805 (1983).
   11In addition, the Governor-General of Grenada—described by the former U.S. ambas-
sador to the Eastern Caribbean as the “sole legitimate source of authority on the island”—

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dent Reagan also made clear that, along with protecting American citi-
zens trapped in Grenada, the mission was intended “to forestall further
chaos” and “to assist in the restoration of conditions of law and order and
of governmental institutions to the island of Grenada.” 

. The
President’s letter to Congress, transmitted “consistent with the War
Powers Resolution,” similarly indicated that, pursuant to his “constitu-
tional authority with respect to the conduct of foreign relations and as
Commander-in-Chief,” he had authorized military action because the
OECS, “concerned by the deteriorating conditions in [its] member State
of Grenada,” had “requested the immediate cooperation of a number of
friendly countries” in an effort to “restore order,” as well as to “protect[]
the lives of the United States citizens” there. Letter to the Speaker of the
House and the President Pro Tempore of the Senate on the Deployment
of United States Forces in Grenada (Oct. 25, 1983), 2 Pub. Papers of
Pres. Ronald 

, 1512–13 (1983).
   Similarly, President George H.W. Bush authorized the use of military
force in the Philippines in 1989 when military leaders seized an air force
base, attacked government facilities, and bombed the presidential palace
as part of a coup attempt. Letter to the Speaker of the House of Represent-
atives and the President Pro Tempore of the Senate on United States
Military Assistance to the Philippines (Dec. 2, 1989), 2 Pub. Papers of
Pres. George Bush 1622, 1622–23 (1989). After the President of the
Philippines “formally requested limited U.S. military assistance to support
her forces as they attempted to put down the coup,” President Bush, acting
“pursuant to [his] constitutional authority with respect to the conduct of
foreign relations and as Commander in Chief,” authorized U.S. military
aircraft to “establish a protective cover . . . to prevent rebel aircraft from
taking off.” Id. at 1623. Although “[n]o rebel aircraft attempted to take


appealed to the United States for help, adding “weight to the legal and political basis for
the invasion.” U.S. Military Actions in Grenada: Implications for U.S. Policy in the
Eastern Caribbean: Hearings Before the Subcomm. on Int’l Sec. and Scientific Affairs
& on W. Hemisphere Affairs of the H. Comm. on Foreign Affairs, 98th Cong. 59 (1988)
(statement of Sally A. Shelton); see also Radio Address to the Nation on International
Stability (Oct. 26, 1985), 2 Pub. Papers of Pres. Ronald 

 (1985)
(noting on the second anniversary of the operation that “Grenada’s Governor-General”
had “appealed for [the United States’s] help to restore order in his country, threatened by
the machinery of dictatorship”).

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

off, and U.S. aircraft did not fire,” President Bush made clear in his War
Powers Resolution notification to Congress that he would be “prepared
. . . to take additional [military] actions” not only “to protect the lives of
Americans” but also, “if requested, to provide further assistance to the
government of the Philippines,” in recognition of the fact that the United
States had “worked . . . over the years to provide assistance to the demo-
cratically elected government of the Philippines.” 

    Along similar lines, after Iraq had invaded Kuwait and was threatening
Saudi Arabia in 1990, and the “Saudi Government had requested [the]
help” of the United States, President Bush deployed the military to “assist
the Saudi Arabian Government in the defense of its homeland.” Address
to the Nation Announcing the Deployment of United States Armed Forces
to Saudi Arabia (Aug. 8, 1990), 2 Pub. Papers of Pres. George Bush 1107,
1107–08 (1990). In his address to the Nation, President Bush explained
that his decision “gr[e]w[] out of the longstanding friendship and security
relationship between the United States and Saudi Arabia” and out of the
principle that “America will stand by her friends.” Id. at 1109. And in his
War Powers Resolution report to Congress, the President indicated that
the U.S. troops would remain “so long as their presence is . . . desired by
the Saudi government to enhance [its] capability . . . to defend the King-
dom.” Letter to Congressional Leaders on the Deployment of United
States Armed Forces to Saudi Arabia and the Middle East (Aug. 9, 1990),
2 Pub. Papers of Pres. George Bush 1116, 1116 (1990). President Bush
also stated that he had taken these actions “pursuant to [his] authority to
conduct our foreign relations and as Commander in Chief.” Id.
    Finally, as referenced above, President Clinton, in coordination with
the deposed, democratically elected President of Haiti, authorized mili-
tary action in Haiti without congressional approval to force the military
dictators from power and “restore Haiti’s legitimate, democratically
elected government.” Address to the Nation on Haiti (Sept. 15, 1994),
2 Pub. Papers of Pres. William J. Clinton 1558, 1558–60 (1994); see also
War Powers Resolution at 37–39. Although an eleventh-hour agreement
with the dictators reduced the risk of direct hostilities, President Clinton
had authorized a hostile military invasion involving 20,000 troops, to be
deployed in conjunction with an international coalition. See 1994 Haiti
Deployment, 18 Op. O.L.C. at 174 n.1, 179 n.10; War Powers Resolution


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at 38; Address to the Nation on Haiti (Sept. 18, 1994), 2 Pub. Papers of
Pres. William J. Clinton 1571, 1571–72 (1994). 12
   In light of this historical practice and our precedent, we believe the
President had the constitutional authority to rely on a national interest in
supporting Iraq, a strategic partner, in ordering targeted airstrikes against
ISIL without congressional approval. Although the President’s support to
the Iraqi government was limited to five particular operations that also
served other national interests, see supra Part II.A.1 and infra Part II.A.3,
the Iraqi government requested the assistance of the United States with
respect to all of those operations, and the President determined that agree-
ing to these requests would materially aid Iraq in its “ongoing campaign
against [ISIL].” August 17 Report to Congress; see August 8 Report to
Congress (noting the Erbil operation would help “stop[] the current ad-
vance on Erbil”); September 1 Report to Congress (noting the action had
been taken “at the request of the Iraqi government”); September 8 Report
to Congress (noting the Haditha Dam airstrikes were undertaken “in
coordination with and at the request of the Iraqi Government” to support
“Iraqi forces in their efforts to retain control of and defend [their] critical
infrastructure”). ISIL, moreover, presents an acute threat to the Iraqi
Government’s control over its country, to law and order within the coun-
try, and to the safety of Iraq’s citizens. See supra Part I. President
Obama’s actions in assisting the Iraqi government’s campaign against
ISIL thus mirror military action taken by past Presidents to suppress
insurrection, maintain order, or restore a rightful government upon an
ally’s or strategic partner’s request, or to answer a friendly government’s
request for help in defending itself from attack.

   12 Responding to an ally’s or partner’s request for assistance bears some resem-

blance to obtaining the consent of a foreign government for using armed force in its
territory, which is a justification under international law for the use of force in such
circumstances. But even leaving aside the differences between responding to an affirma-
tive request from an ally or partner and seeking consent from a country for military action
the United States seeks to initiate, nothing in the presidential statements discussed in the
text suggests that these Presidents were invoking assistance to an ally or partner primarily
as an international law justification for their actions. Indeed, as we noted in the text,
Presidents have included assistance to allies or strategic partners as a reason for taking
military action in reports sent to Congress “consistent with the War Powers Resolution,”
which requires an explanation of the domestic “constitutional and legislative authority”
pursuant to which the President has authorized military action. 

(a).

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

   In addition, Iraq—like many of the allies or partners Presidents assisted
in the examples described above—is a country of particular strategic
importance to the United States and one that the United States has aided
in the past and has made an ongoing commitment to assist. The use of
military force to assist allies in general is consistent with the current U.S.
national security strategy, which expressly states that “[t]he foundation of
the United States, regional, and global security will remain America’s
relations with our allies, and our commitment to their security is unshaka-
ble.” National Security Strategy 41 (May 2010), http://nssarchive.us/
NSSR/2010.pdf. And with respect to Iraq in particular, the United States
has a recent history of providing assistance, including military assistance
authorized by Congress, as Iraq works to establish itself as a stable coun-
try in a volatile and strategically important region. See Iraq AUMF; supra
Part I (discussing surge). Although the United States withdrew its troops
from Iraq in 2011, it simultaneously committed to “continue to foster
close cooperation concerning defense and security arrangements” and to
“improve and strengthen the security and stability in Iraq.” Strategic
Framework Agreement at 2–3; see also U.S. Dep’t of Def., News Tran-
script, Joint Press Conference by Secretary Hagel and Minister Johnston
in Sydney, Australia (Aug. 11, 2014) (Secretary Hagel), https://dod.
defense.gov/News/Transcripts/Transcript-View/Article/606908/joint-
press-conference-by-secretary-hagel-and-minister-johnston-in-sydney-
austr (“[T]he [P]resident has also made it clear we’re going to support the
Iraqi security forces in—in every way we can, as they request assistance
there.”). In addition, as the President has explained, a stable Iraq will
permit the United States “to craft [a] . . . joint counterterrorism strategy”
with “the Iraqi Government [and] also with regional actors . . . beyond
the Middle East.” Remarks on the Situations in Iraq and Ferguson, Mis-
souri, and an Exchange with Reporters, Daily Comp. Pres. Doc. No.
DCPD201400615, at 4 (Aug. 18, 2014); see also John Kerry, U.S. Dep’t
of State, Press Statement, U.S. Welcomes Important Step in Iraq’s Gov-
ernment Formation Process (Aug. 11, 2014), https://2009-2017.state.gov/
secretary/remarks/2014/08/230506.htm (emphasizing that “[t]he United
States will continue to . . . stand with the Iraqi people in their fight
against terrorism”). The President thus had the constitutional authority to
rely on a national interest in supporting Iraq, a strategic partner, in order-
ing targeted airstrikes against ISIL without congressional approval.


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                                     3.

   The third national interest cited by President Obama—relevant in par-
ticular to the airstrikes near Mount Sinjar, the Mosul Dam, Amirli, and the
Haditha Dam—is an interest in averting humanitarian catastrophe. See
President Obama August 7 Statement (citing the need to prevent a “poten-
tial act of genocide” at Mount Sinjar); August 8 Report to Congress
(explaining that the airstrikes around Mount Sinjar were authorized to
“protect the civilians trapped there”); August 17 Report to Congress
(noting the failure of the Mosul Dam could “threaten the lives of large
numbers of civilians”); September 1 Report to Congress (noting that the
Amirli airstrikes would “address the emerging humanitarian crisis and
protect the civilians trapped” in that town); September 8 Report to Con-
gress (noting the danger to “large numbers of Iraqi civilians”). We believe
it was reasonable for the President, in exercising his constitutional author-
ity as Commander in Chief and Chief Executive, to rely on this humani-
tarian interest, at least in combination with a national interest in protect-
ing American citizens and property or supporting a strategic partner, as a
basis for conducting military action without prior authorization from
Congress.
   The United States places great importance on protecting innocent lives
and reducing suffering around the world. In a recent presidential directive,
for example, President Obama recognized that “[p]reventing mass atroci-
ties and genocide is a core national security interest and a core moral
responsibility of the United States.” Office of the Press Secretary, The
White House, PSD-10, Presidential Study Directive on Mass Atrocities
(Aug. 4, 2011), https://obamawhitehouse.archives.gov/the-press-office/
2011/08/04/presidential-study-directive-mass-atrocities. Consistent with
that interest, the United States has ratified and implemented, through the
Genocide Convention Implementation Act of 1987, 

 Stat. 3045 (1988), the Convention on the Prevention and Punishment
of the Crime of Genocide, Dec. 9, 1948, 78 U.N.T.S. 277, which affirms
that the contracting parties will “undertake to prevent” genocide and
recognizes that “in order to liberate mankind from such an odious
scourge, international co-operation is required,” 

 pmbl., art. I; see also
Application of Convention on Prevention and Punishment of Crime of
Genocide (Bosn. & Herz. v. Serb. & Montenegro), Judgment, 2007 I.C.J.
47, ¶ 165 (Feb. 26) (finding that “the contracting parties have a direct
                                    112
        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

obligation to prevent genocide”). The United States has also made clear
that preventing mass atrocities may in some instances require the use of
military force. See, e.g., National Security Strategy 48 (May 2010) (“In
the event that prevention fails, the United States will work both multilat-
erally and bilaterally to mobilize diplomatic, humanitarian, financial,
and—in certain instances—military means to prevent and respond to
genocide and mass atrocities.”).
   Consistent with these policies, Presidents have cited humanitarian con-
cerns as an important national interest supporting multiple U.S. military
deployments in the past, including those in Haiti in 1994, the former
Yugoslavia in 1995, and Libya in 2011. See, e.g., Letter to Congressional
Leaders on Deployment of United States Armed Forces to Haiti (Sept. 18,
1994), 2 Pub. Papers of Pres. William J. Clinton 1572, 1572 (1994) (“The
deployment of U.S. Armed Forces into Haiti is justified by United States
national security interests” including “stop[ping] the brutal atrocities that
threaten tens of thousands of Haitians[.]”); Letter to Congressional Lead-
ers on the Deployment of United States Military Forces for Implementa-
tion of the Balkan Peace Process (Dec. 21, 1995), 2 Pub. Papers of Pres.
William J. Clinton 1917, 1917–18 (1995) (“I authorized these deploy-
ments . . . as part of our commitment to secure the peace and halt the
tragic loss of life in the former Yugoslavia.”); Office of the Press Secre-
tary, The White House, Letter from the President Regarding the Com-
mencement of Operations in Libya (Mar. 21, 2011) (“Libya Report to
Congress”), https://obamawhitehouse.archives.gov/the-press-office/2011/
03/21/letter-president-regarding-commencement-operations-libya (notify-
ing Congress of the commencement of operations “to prevent a humani-
tarian catastrophe”).
   Indeed, in some past military deployments, a humanitarian purpose ap-
pears to have been one of the primary reasons for the President’s decision
to act. In March 1999, for example, when President Clinton, together with
certain NATO allies, launched airstrikes against the Serbian forces and
military infrastructure of the Federal Republic of Yugoslavia to protect
civilians in Kosovo, humanitarian purposes were the central focus of the
mission. As President Clinton weighed his military options in the region,
he stated that “[o]ur objective in Kosovo remains clear: to stop the killing
and achieve a durable peace that restores Kosovars to self-government.”
Remarks on the Situation in Kosovo (Mar. 22, 1999), 1 Pub. Papers of

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Pres. William J. Clinton 426, 426 (1999). And when he announced the
airstrikes, President Clinton notified Congress that he was doing so for the
principal purposes of emphasizing to Serbian leaders “the imperative of
reversing course” in their offensive against civilians in Kosovo; “to deter
an even bloodier offensive against innocent civilians in Kosovo; and, if
necessary, to seriously damage the Serbian military’s capacity to harm the
people of Kosovo.” Letter to Congressional Leaders Reporting on Air-
strikes Against Serbian Targets in the Federal Republic of Yugoslavia
(Serbia and Montenegro) (Mar. 26, 1999), 1 Pub. Papers of Pres. William
J. Clinton 459, 459 (1999). 13 Two weeks later, President Clinton reaf-
firmed these objectives when he stated that he would “continue to intensi-
fy our actions to achieve the objectives . . . described” in the previous
report to Congress, and to “support the international relief efforts being
conducted in the region.” Letter to Congressional Leaders Reporting on
Airstrikes Against Serbian Targets in the Federal Republic of Yugoslavia
(Serbia and Montenegro) (Apr. 7, 1999), 1 Pub. Papers of Pres. William J.
Clinton 516, 516 (1999). The President underscored the humanitarian
nature of the operation by ordering the deployment of forces to Albania
and Macedonia “to support humanitarian disaster relief operations for the
Kosovar refugees.” 

 And shortly thereafter, he described his actions in
Kosovo and surrounding areas as an effort “to stand against ethnic cleans-
ing, save lives, and bring peace in Kosovo.” Remarks Following a Meet-
ing with Congressional Leaders and an Exchange with Reporters (Apr.
13, 1999), 1 Pub. Papers of Pres. William J. Clinton 546, 546 (1999).
   Similarly, President George H.W. Bush’s deployment of more than
25,000 troops to war-torn and divided Somalia during a widespread fam-
ine in 1992 was undertaken “to address a major humanitarian calamity,
avert related threats to international peace and security, and protect the
safety of Americans and others engaged in relief operations.” Letter to
Congressional Leaders on the Situation in Somalia (Dec. 10, 1992),
2 Pub. Papers of Pres. George Bush 2179, 2179–80 (1992–93); see Ad-
dress to the Nation on the Situation in Somalia (Dec. 4, 1992), 2 Pub.
Papers of Pres. George Bush 2174, 2175 (1992–93) (“It’s now clear that

   13 Although the notification to Congress also mentions other concerns—including con-

cerns about regional stability that we cited in our Libya opinion, see Military Force in
Libya, 35 Op. O.L.C. at 34–35—the notification makes clear that the mission was princi-
pally a humanitarian one.

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

military support is necessary to ensure the safe delivery of the food Soma-
lis need to survive.”). In his address to the Nation, President Bush said:
“Let me be very clear: Our mission is humanitarian[.]” Address to the
Nation on Situation in Somalia, 2 Pub. Papers of Pres. George Bush at
2175 (1992–93); see also Michael R. Gordon, Mission to Somalia: U.S. Is
Sending Large Force as Warning to Somali Clans, N.Y. Times, Dec. 5,
1992, at 5 (noting the Pentagon had issued an “official ‘mission state-
ment’ for the operation, which underscored that the purpose of the inter-
vention is to provide humanitarian aid”). The mission’s purpose was thus
not simply to protect the American citizens already in Somalia and to
“facilitate the safe and orderly deployment of U.N. peacekeeping forces in
Somalia,” but also “to restore the flow of humanitarian relief to those
areas of Somalia most affected by famine and disease.” Military Forces in
Somalia, 16 Op. O.L.C. at 6. In explaining why such an expansive U.S.
military action was needed, President Bush emphasized that “[o]nly the
United States has the global reach to place a large security force on the
ground in such a distant place quickly and efficiently and thus save thou-
sands of innocents from death.” Address to the Nation on the Situation in
Somalia, 2 Pub. Papers of Pres. George Bush at 2175 (1992–93). Pres-
ident Clinton also reiterated the humanitarian nature of the Somalia mis-
sion when the deployment ended. See Remarks on Welcoming Military
Personnel Returning from Somalia (May 5, 1993), 1 Pub. Papers of Pres.
William J. Clinton 565, 565 (1993) (noting it was “the largest humanitari-
an relief operation in history” and that “tens of thousands would have
died” if the U.S. had not acted).
   While Presidents have often stressed the humanitarian purposes under-
lying military actions taken abroad, this Office’s analysis of these actions
has frequently emphasized other relevant national interests, such as
regional stability or the protection of American lives. See, e.g., Military
Force in Libya, 35 Op. O.L.C. at 27 (emphasizing “important U.S. inter-
ests in preventing instability in the Middle East and preserving the credi-
bility and effectiveness of the United Nations Security Council”); Pro-
posed Bosnia Deployment, 19 Op. O.L.C. at 332–33 (emphasizing sup-
port for the United Nations and the North Atlantic Treaty Organization,
as well as the need to preserve regional stability); 1994 Haiti Deploy-
ment, 18 Op. O.L.C. at 177–79 (highlighting the fact that the operation
took place with the consent of the legitimate government). But despite

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focusing on other national interests, our opinions have often expressly
noted the humanitarian purpose of those deployments. And in so doing,
we have never suggested that the goal of preventing humanitarian catas-
trophes could not be an important national interest supporting the use of
military force abroad. See Military Force in Libya, 35 Op. O.L.C. at 23,
35; Proposed Bosnia Deployment, 19 Op. O.L.C. at 329; 1994 Haiti
Deployment, 18 Op. O.L.C. at 177.
   We have also more than once suggested that, when a military deploy-
ment is undertaken in part to protect American citizens abroad, its scope
can legitimately be expanded to achieve broader humanitarian objectives.
In analyzing the legality of the deployment of U.S. forces to Somalia, for
example, we began with the national interest in the protection of U.S.
persons, see Military Forces in Somalia, 16 Op. O.L.C. at 6, but then went
on to determine that the President’s power to deploy forces abroad was
not “strictly limited to the protection of American citizens,” id. at 11.
“Past military interventions,” we explained, “extended to the protection of
foreign nationals” and “provide precedent for action to protect endangered
Somalians and other non-United States citizens.” Id. (citing, among other
examples, President Johnson’s ordering of military intervention in the
Dominican Republic to “preserve the lives of American citizens and
citizens of a good many other nations” and President McKinley’s dispatch
of 5,000 troops to China during the Boxer Rebellion to rescue the be-
sieged foreign legations, including both U.S. and foreign contingents, in
Beijing (internal quotation marks omitted)); see also Right to Protect at
65 (troops landed in Uruguay in 1868 “for the protection of foreign resi-
dents” generally during an insurrection); id. at 120 (troops sent to Nicara-
gua in 1912 to help the Nicaraguan government protect American citizens
and “all inhabitants” of the country during an attempted revolution (inter-
nal quotation marks omitted)). We reached a similar conclusion in 2004,
determining that “[w]hen the armed forces [we]re deployed [to Haiti] for
the protection of American citizens and property, their mission once
deployed” did not need to be “so narrowly limited,” but rather could
extend to the protection of Haitians and other innocent civilians. 2004
Haiti Deployment, 28 Op. O.L.C. at 32. 14


   14 Although the engagements in Somalia and Haiti had the reinforcement of U.N. reso-
lutions authorizing force, our opinions did not suggest that a President could expand the

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   In light of these precedents, we believe it was reasonable for the Presi-
dent to rely on a national interest in preventing humanitarian catastrophe,
at least in combination with an interest in protecting Americans or sup-
porting an ally or strategic partner, as a justification for conducting
airstrikes against ISIL’s positions around Mount Sinjar, the Mosul Dam,
Amirli, and the Haditha Dam. As discussed above, the President deter-
mined that the situation on Mount Sinjar presented “the prospect of
violence on a horrific scale,” involving “a potential act of genocide” that
the United States had “unique capabilities to help avert.” President
Obama August 7 Statement; cf. Address to the Nation on the Situation in
Somalia, 2 Pub. Papers of Pres. George Bush at 2175 (1992–93) (noting
that, in Somalia, “[o]nly the United States” could “save thousands of
innocents from death”). This concern was shared by U.N. officials, who
warned that a “humanitarian tragedy [wa]s unfolding in Sinjar.” UN
Daily News, UN Warns of “Humanitarian Tragedy” as Militants Seize
Town in Northern Iraq (Aug. 4, 2014), http://www.un.org/News/dh/pdf/
english/2014/04082014.pdf; see also Security Council August 5 Press
Release (expressing “deep concern” about the thousands of Iraqis, many
from the Yezidi community, displaced by ISIL and “in urgent need of
humanitarian assistance”). Similarly, the failure of either the Mosul Dam
or the Haditha Dam could have unleashed flood waves capable of killing
large numbers of innocent civilians and endangering or displacing hun-
dreds of thousands of others, in cities from Mosul to Baghdad. See Au-
gust 17 Report to Congress; Mosul Dam Letter; September 8 Report to
Congress; NSC September 7 Statement; see also Ellison, An Unprece-
dented Task, 63 Int’l Water Power & Dam Construction at 50–51 (noting
the failure of the Mosul Dam could potentially kill a half-million civil-
ians). And in Amirli, the President likewise identified an “emerging
humanitarian crisis” caused by ISIL’s siege of the town, September 1
Report to Congress, an assessment that reflected the State Department’s


scope of a mission for humanitarian reasons only if a U.N. resolution was in effect. See
2004 Haiti Deployment, 28 Op. O.L.C. at 33; Military Forces in Somalia, 16 Op. O.L.C.
at 7. Moreover, although the U.N. Security Council has not passed a resolution authoriz-
ing the use of force in Iraq, it has called on the international community “to support the
Government and people of Iraq and to do all it can to help alleviate the suffering of the
population affected by the current conflict in Iraq.” Security Council August 7 Press
Release.

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concern about the “dire conditions for the mainly Turkmen population,”
State Department August 28 Daily Press Briefing, and that was consistent
with calls by U.N. officials for “immediate action” to alleviate the “des-
perate” and “inhuman conditions” in Amirli and prevent a “possible
imminent massacre” of the town’s citizens, see UN News, Iraqi Civil-
ians Suffering “Horrific” Persecution, Ethnic Cleansing—UN Rights
Chief (Aug. 25, 2014), https://news.un.org/en/story/2014/08/475812-
iraqi-civilians-suffering-horrific-persecution-ethnic-cleansing-un-rights-
chief; UN News, Iraq: UN Envoy Calls for Immediate Action to Avert
Possible “Massacre” in Northern Town (Aug. 23, 2014), https://news.un.
org/en/story/2014/08/475762-iraq-un-envoy-calls-immediate-action-avert-
possible-massacre-northern-town. In all four instances, U.S. airstrikes
were designed to help Iraqi and aligned forces prevent the humanitarian
catastrophes that were unfolding, either by mitigating ISIL’s threat, per-
mitting the delivery of humanitarian aid, or both. Given these circum-
stances, we think the President reasonably invoked a national interest in
preventing humanitarian catastrophe, in combination with a national
interest in protecting American citizens and property or supporting a
strategic partner, to justify deploying military forces abroad. 15

                                            B.

   We next consider whether the anticipated nature, scope, and duration of
the airstrike operations discussed in this opinion were sufficiently limited
so as not to require prior congressional approval under the Declaration of
War Clause. As we have previously explained, determining whether a
military engagement amounts to a “war” for constitutional purposes
involves a “fact-specific assessment of the ‘anticipated nature, scope, and
duration’ of the planned military operations,” analyzed in light of the
applicable historical precedent. Military Force in Libya, 35 Op. O.L.C. at
31 (quoting 1994 Haiti Deployment, 18 Op. O.L.C. at 179). Here, we


   15 Our conclusion addresses only the President’s domestic legal authority to engage in
such military intervention without prior congressional approval. We do not address the
validity of humanitarian intervention as a justification for the use of force under interna-
tional law. See, e.g., Paul R. Williams et al., Preventing Mass Atrocity Crimes: The Re-
sponsibility to Protect and the Syria Crisis, 45 Case W. Res. J. Int’l L. 473, 479–80 (2012)
(noting the controversy surrounding humanitarian intervention in international law).

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believe the anticipated nature, scope, and duration of the operations at
issue were sufficiently limited so as not to constitute a “war.”
   Military actions generally rise to the level of “war” for constitutional
purposes only when they involve “prolonged and substantial military
engagements, typically involving exposure of U.S. military personnel to
significant risk over a substantial period.” Id. Certain factors reduce the
likelihood that a military engagement will amount to a “war” in the con-
stitutional sense. For example, military operations that do not include the
introduction of ground troops are less likely to constitute a “war.” See id.
at 38; Proposed Bosnia Deployment, 19 Op. O.L.C. at 333. 16 In addition,
we have previously suggested that where an “operation does not aim at
the conquest or occupation of territory” or seek to “impos[e] through
military means a change in the character of the political regime,” the
operation’s more limited aims will likely reduce the risk of resistance to
the U.S. deployment and decrease the time needed to fulfill those aims.
Proposed Bosnia Deployment, 19 Op. O.L.C. at 332. Both the lack of
ground troops and the more limited goal of an operation also limit the
“antecedent risk that United States forces” will “suffer or inflict substan-
tial casualties as a result of the deployment.” 1994 Haiti Deployment, 18
Op. O.L.C. at 179.
   Consistent with these principles, we advised in 2011 that the conduct of
limited airstrikes and associated support missions in Libya for the purpose


   16 We do not mean to imply that contemplated deployments of ground forces—even in
substantial numbers—necessarily constitute “wars” for constitutional purposes. For
example, in 1994, we concluded that the planned deployment of 20,000 troops to Haiti to
oust military dictators and reinstall the legitimate government was not a “war,” placing
great weight on “the limited antecedent risk that United States forces would encounter
significant armed resistance or suffer or inflict substantial casualties as a result of the
deployment.” 1994 Haiti Deployment, 18 Op. O.L.C. at 179. And in 1995, we concluded
that the planned deployment of about 20,000 ground troops to Bosnia and Herzegovina to
ensure compliance with a peace agreement was not a “war.” Proposed Bosnia Deploy-
ment, 19 Op. O.L.C. at 332–33. We acknowledged that the deployment of ground troops
was “an essentially different, and more problematic, type of intervention” than air or
naval operations, because of the increased risk of casualties and the greater difficulty of
withdrawing ground forces, but nevertheless found that that concern was outweighed by
the fact that the deployment was at the invitation of warring parties to support the agree-
ment they had reached and thus it was “reasonably possible that little or no resistance to
the deployment w[ould] occur.” Id.

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of preventing regional instability and preserving the credibility and effec-
tiveness of the U.N. Security Council did not amount to a “war” in the
constitutional sense. Military Force in Libya, 35 Op. O.L.C. at 37–39. The
U.S. mission had at first targeted the Libyan regime’s “air defense sys-
tems, command and control structures, and other capabilities . . . used to
attack civilians and civilian populated areas,” and had then shifted to
providing support for a NATO-led effort to enforce a no-fly zone and
otherwise protect civilians in Libya. 

 at 25–26 (internal quotation
marks omitted). We compared this operation to two prior campaigns
conducted without prior congressional authorization—a series of no-fly
zone patrols and periodic airstrikes in Bosnia that had lasted for more than
two years prior to the deployment of ground troops in 1995 and a two-
month NATO bombing campaign in Yugoslavia in 1999—and concluded
that the operations in Libya similarly fell short of requiring a congres-
sional declaration of war. We reached this conclusion in part based on the
President’s assurance that—as in the air campaigns in Bosnia and Yugo-
slavia—ground troops would not be deployed, which meant that “[t]he
planned operations [would] avoid[] the difficulties of withdrawal and
risks of escalation that may attend commitment of ground forces.” 

. We also based our conclusion on the “limited means, objectives, and
intended duration” of the mission, explaining that the proposed action
“did not ‘aim at the conquest or occupation of territory,’” but instead was
“‘in support of international efforts to protect civilians and prevent a
humanitarian disaster.’” 

 (quoting Proposed Bosnia Deployment, 19
Op. O.L.C. at 332; Libya Report to Congress).
   For similar reasons, we do not believe that the operations addressed in
this opinion constituted a “war” in the constitutional sense. President
Obama made clear that—aside from a rejected proposal to use ground
troops to help extract the trapped Yezidis, see supra note 4—the opera-
tions would be restricted to airstrikes and associated support missions.
“American combat troops,” the President explained, “will not be return-
ing to fight in Iraq.” Office of the Press Secretary, The White House,
Weekly Address: American Operations in Iraq (Aug. 9, 2014), https://
obamawhitehouse.archives.gov/the-press-office/2014/08/09/weekly-
address-american-operations-iraq; see also Office of the Press Secretary,
The White House, Press Briefing by Principal Deputy Press Secretary
Eric Schultz and Deputy National Security Advisor Ben Rhodes (Aug.

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        Targeted Airstrikes Against the Islamic State of Iraq and the Levant

13, 2014), https://obamawhitehouse.archives.gov/the-press-office/2014/
08/13/press-briefing-principal-deputy-press-secretary-eric-schultz-and-
deputy- (noting, in response to questions about the possibility of ground
troops assisting in an evacuation of Mount Sinjar, that President Obama
had “ruled out . . . reintroducing U.S. forces into combat, on the ground,
in Iraq”). Thus, like our efforts in Libya, these operations were designed
to “avoid the difficulties of withdrawal and risks of escalation that may
attend commitment of ground forces.” Military Force in Libya, 35 Op.
O.L.C. at 38.
   Moreover, these operations furthered “limited mission[s]” with well-
defined and narrow objectives. Proposed Bosnia Deployment, 19 Op.
O.L.C. at 332; see also, e.g., Military Force in Libya, 35 Op. O.L.C. at 38.
In the airstrikes directed at ISIL positions around Mount Sinjar and Erbil,
President Obama directed U.S. military forces to conduct operations that
were “limited in their scope and duration as necessary to protect Ameri-
can personnel in Iraq by stopping the current advance on Erbil by [ISIL]
and to help forces in Iraq as they fight to break the siege of Mount Sinjar
and protect the civilians trapped there.” August 8 Report to Congress; see
also, e.g., President Obama August 7 Statement (describing the opera-
tions’ scope and purpose). The later operations against ISIL positions
around the Mosul Dam, Amirli, and the Haditha Dam were similarly
limited to specific, narrowly defined objectives involving the protection
of Americans, assistance to Iraq, and the prevention of humanitarian
catastrophe. See August 17 Report to Congress (indicating that the Presi-
dent had authorized “targeted air strikes to support operations by Iraqi
forces to recapture the Mosul Dam”); September 1 Report to Congress
(stating that operations related to Amirli would be “limited in their scope
and duration as necessary to address this emerging humanitarian crisis and
protect the civilians trapped in” the town); September 8 Report to Con-
gress (indicating the operations would “be limited in their scope and
duration as necessary to address th[e] threat [to Haditha Dam] and prevent
endangerment of U.S. personnel and facilities and large numbers of Iraqi
civilians”). It was thus anticipated that the specific operations at issue
would be confined to narrow geographic regions within Iraq and would
serve limited and largely “protective purposes” that did “not aim at the
conquest or occupation of territory” or “at imposing through military
means a change in the character of a political regime.” Proposed Bosnia

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Deployment, 19 Op. O.L.C. at 332. Those factors made it less likely that
the operations would be of a lengthy duration or that, as a result of the
operations, the United States would “find itself involved in extensive or
sustained hostilities.” Id.; see also 1994 Haiti Deployment, 18 Op. O.L.C.
at 173 (anticipated military operations did not amount to a “war” in part
because they “did not involve the risk of major or prolonged hostilities”).
   Because of the absence of ground troops and the limited nature of the
specific missions involved, the anticipated operations discussed in this
opinion did not, in our view, amount to a “prolonged and substantial
military engagement[] . . . involving exposure of U.S. military personnel
to significant risk over a substantial period.” Military Force in Libya, 35
Op. O.L.C. at 31. We therefore conclude that the “anticipated nature,
scope, and duration” of those military operations did not rise to the level
of a “war” within the meaning of the Declaration of War Clause.

                                     III.

   For the reasons set forth above, we conclude that President Obama had
the constitutional authority to order the targeted airstrike operations
against ISIL described above. The President reasonably determined that
these military operations furthered important national interests in protect-
ing American lives, assisting an ally or strategic partner at its request, and
preventing humanitarian catastrophe; and the anticipated nature, scope,
and duration of the operations were sufficiently limited so as not to re-
quire prior congressional approval.

                                     KARL R. THOMPSON
                           Principal Deputy Assistant Attorney General
                                     Office of Legal Counsel




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