Article I, Section 8, Clause 11:

[The Congress shall have Power . . . ] To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water; . . .

The end of World War II brought changes in U.S. policy and practice toward declarations of war and the exercise of military action more generally. Congress has not formally declared war since the Second World War and has instead relied solely on statutory authorizations for the use of military force when permitting the President to engage in armed conflict. The Second World War’s conclusion also brought an end to a historical pattern in which the United States’ buildup of forces for war was followed by extensive demobilization and return of troops to the homeland.1 After World War II, the United States permanently stationed U.S. troops in foreign countries, assumed greater responsibility for global security, and made defense pacts and military commitments with its allies, such as those in the North Atlantic Treaty Organization (NATO).2 Concerns over Soviet expansion and influence also led to the Cold War in which the United States adopted a strategy to contain Soviet power throughout the world.3

These dynamics undermined clear distinctions between states of war and periods of peace and led to interbranch debate over presidential power to deploy and station troops abroad.4 In what was called at the time the “Great Debate,” Congress engaged with Truman Administration over whether congressional authorization was necessary for the President to send 100,000 U.S. Army troops to Western Europe to demonstrate support for NATO and counter the threat of Soviet expansion.5 The Senate was considering a resolution prohibiting the assignment of forces until Congress formulated a policy on the troop transfer,6 but President Truman took the position that his constitutional power as Commander-in-Chief authorized him to send troops anywhere in the world.7 The debate was ultimately resolved through a compromise resolution that authorized the transfer but required congressional approval for troops beyond four divisions.8

The North Atlantic Treaty also gave rise to constitutional questions of whether the treaty’s requirement for collective self-defense would usurp Congress’s power to declare war. Under Article 5 of the treaty, “an armed attack against one more [NATO country] in Europe or North America shall be considered an attack against them all . . . .” 9 During Senate hearings, Secretary of State Dean Acheson stated the view that Article 5 would not infringe on the declare war power because it commits NATO countries to take measures they deem necessary, but “does not mean that the United States would automatically be at war . . . .” 10 With this assurance, the Senate gave its advice and consent to ratification of the North Atlantic Treaty, although the Senate declined to attach an understanding to its resolution of ratification confirming Acheson’s interpretation.11

The Charter of the United Nations (UN) also raised questions about how post-war international institutions would integrate into the constitutional system.12 The creation of the UN Security Council, which was empowered to ensure global peace and security,13 prompted debate over whether a Security Council resolution can function as a constitutional substitute for a congressional declaration of war or authorization for use of military force.14 The Security Council’s place in the Constitution’s war powers scheme would come to the fore when later presidents, including President Truman during the Korean War, cited its resolutions as a part of the legal basis to initiate military action without first seeking congressional authorization.15

(discussing the role of Security Council resolutions in past military interventions and in providing legal support for an air campaign in Libya).

Footnotes

1

See, e.g., Matthew C. Waxman, The Power to Wage War Successfully, 117 Colum. L. Rev. 613, 677–78 (2017).

2

See, e.g., Statement of Hon. Nicholas Katzenbach, Under Sec’y of State, to the S. Foreign Relations Comm. (Aug. 17, 1967), reprinted in Congress, the President, and War Powers, Hearings before the Subcomm. on National Security Policy and Scientific Developments of the H. Comm. on Foreign Affairs, 91st Cong. 553, 554 (1970) (discussing the “revolutionary change in the political structure of the world—and of the relative importance of foreign affairs to the United States.” ); 2 Am. Mil. Hist., The U.S. army in a Global Era, at 201–10 (2d. ed. 2005), .

3

See NSC-68, A Report to the Nat’l Sec. Council by the Executive Secretary on the United States Objectives and Programs in Nat’l Sec. (Apr. 14, 1950), >https://www.jstor.org/stable/44641594; 2 Am. Mil. Hist., supra note 2, at 218–19.

4

See, e.g., Stephen M. Griffin, Long Wars and Constitution 6 (2013).

5

See Assignment of Ground Forces of the United States to Duty in the European Area, Hearings before the S. Comm. on Foreign Relations and S. Comm. on Armed Services, 82nd Cong. 56 (1952) [hereinafter Assignment of Ground Forces Hearing].

6

82 Cong. Rec. 94 (1951).

7

See Foreign Relations of the United States, 1951, European Security and the German Question, Volume 3, pt. 1, Dep’t of State: Office of the Historian, >https://history.state.gov/historicaldocuments/frus1951v03p1/d11 (last visited Sept. 20, 2024). See also Assignment of Ground Forces Hearing, supra note 5, at 9 (statement of U.S. Sec’y of State Dean Acheson) ( “Not only has the President the authority to use the armed forces in carrying out the broad foreign policy of the United States implementing treaties, but it is equally clear that this authority may not be interfered with by the Congress in the exercise of powers which it has under the Constitution.” ).

8

82 Cong. Rec. 3096, 3282 (1951).

9

North Atlantic Treaty art. V, Apr. 4, 1949, 63 Stat. 224, 34 U.N.T.S. 243.

10

North Atlantic Treaty (pt. 1): Hearings Before the Senate Comm. on Foreign Relations, 81st Cong. 11 (1949).

11

95 Cong. Rec. 9916 (1949). For background on the Senate’s ability to conditionally consent to treaties subject to reservations, understandings, and declarations, see Stephen P. Mulligan, Cong. Rsch. Serv., IF12208, Reservations, Understandings, Declarations, and Other Conditions to Treaties (2022), >https://crsreports.congress.gov/product/pdf/IF/IF12208.

12

UN Charter. See also .

13

UN Charter art. 24(1).

14

Whereas some observers argue that Presidents are not required to obtain congressional authorization when the Security Council approves international use of force, others contend that the Security Council is not the functional equivalent to Congress and cannot supersede the Constitution’s domestic legal processes. See, e.g., Curtis A. Bradley, International Law in the U.S. Legal System 296–97 (1st ed. 2013) (summarizing the debate).

15

See §

International Police Action and the Korean War.; Military Force in Libya,

35 Op. O.L.C., slip op. at 10 (2011)

(discussing the role of Security Council resolutions in past military interventions and in providing legal support for an air campaign in Libya).