Declaration of war by the United States

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Franklin D. Roosevelt signs the declaration of war against Japan on December 8, 1941

A declaration of war is a formal declaration issued by a national government indicating that a state of war exists between that nation and another. The document Declarations of War and Authorizations for the Use of Military Force: Historical Background and Legal Implications gives an extensive listing and summary of statutes which are automatically engaged upon the US declaring war.

For the United States, Article One, Section Eight of the Constitution says "Congress shall have power to ... declare War." However, that passage provides no specific format for what form legislation must have in order to be considered a "declaration of war" nor does the Constitution itself use this term. In the courts, the United States Court of Appeals for the First Circuit, in Doe v. Bush, said: "[T]he text of the October Resolution itself spells out justifications for a war and frames itself as an 'authorization' of such a war."[1] in effect saying an authorization suffices for declaration and what some may view as a formal Congressional "Declaration of War" was not required by the Constitution.

The last time the United States declared war on any nation was in 1942, when war was declared against Axis-allied Hungary, Bulgaria, and Romania, because President Franklin Roosevelt thought it was improper to engage in hostilities against a country without a declaration of war. Since then, every American president has used military force without a declaration of war.[2]

This article will use the term "formal declaration of war" to mean Congressional legislation that uses the phrase "declaration of war" in the title. Elsewhere, this article will use the terms "authorized by Congress," "funded by Congress" or "undeclared war" to describe other such conflicts.


The United States has formally declared war against foreign nations five separate times, each upon prior request by the President of the United States. Four of those five declarations came after hostilities had begun.[3] James Madison reported that in the Federal Convention of 1787, the phrase "make war" was changed to "declare war" in order to leave to the Executive the power to repel sudden attacks but not to commence war without the explicit approval of Congress.[4] Debate continues as to the legal extent of the President's authority in this regard. Public opposition to American involvement in foreign wars, particularly during the 1930s, was expressed as support for a Constitutional Amendment that would require a national referendum on a declaration of war.[5] Several Constitutional Amendments, such as the Ludlow Amendment, have been proposed that would require a national referendum on a declaration of war.

After Congress repealed the Gulf of Tonkin Resolution in January 1971 and President Richard Nixon continued to wage war in Vietnam, Congress passed the War Powers Resolution (Pub.L. 93–148) over the veto of Nixon in an attempt to rein in some of the president's claimed powers. The War Powers Resolution proscribes the only power of the president to wage war which is recognized by Congress.[6]

Declarations of war[edit]


The table below lists the five wars in which the United States has formally declared war against eleven foreign nations.[7] The only country against which the United States has declared war more than once is Germany, against which the United States has declared war twice (though a case could be made for Hungary as a successor state to Austria-Hungary).

In World War II, the Japanese attacked Pearl Harbor on December 7, 1941. Germany and Italy, led respectively by Adolf Hitler and Benito Mussolini, declared war on the United States, and the U.S. Congress responded in kind.[8][9]

War Declaration Opponent(s) Date of declaration Votes President Result
Senate House
War of 1812 Declaration of War upon the U.K.  United Kingdom June 18, 1812 19–13 79–49 James Madison Treaty of Ghent (December 24, 1814)
Mexican–American War "An Act providing for the Prosecution of the existing War between the United States and the Republic of Mexico."[10] Mexico May 13, 1846 40–2 173–14 James K. Polk Treaty of Guadalupe Hidalgo (February 2, 1848)
Spanish–American War Declaration of War upon Spain Spain April 25, 1898 42–35 310–6 William McKinley Treaty of Paris (December 10, 1898)
World War I Declaration of War upon Germany  Germany April 6, 1917 82–6 373–50 Woodrow Wilson Treaty of Berlin (August 25, 1921)
Declaration of War upon Austria-Hungary[11][12]  Austria-Hungary December 7, 1917 74–0 365–1 1921 U.S.–Austrian Peace Treaty (August 24, 1921), 1921 U.S.-Hungarian Peace Treaty (August 29, 1921)
World War II Declaration of War upon Japan  Japan December 8, 1941 82–0 388–1 Franklin D. Roosevelt V-J Day, Japanese Instrument of Surrender (September 2, 1945), Treaty of San Francisco (September 8, 1951)
Declaration of War upon Germany  Germany December 11, 1941 88–0 393–0 V-E Day, German Instrument of Surrender (May 8, 1945), Treaty on the Final Settlement with Respect to Germany (September 12, 1990), Treaty of Vienna with Austria (May 15, 1955)
Declaration of War upon Italy  Italy 90–0 399–0 Paris Peace Treaty (February 10, 1947)
Declaration of War upon Bulgaria  Bulgaria June 5, 1942 73–0 357–0
Declaration of War upon Hungary[11]  Hungary 360–0
Declaration of War upon Romania[11]  Romania 361–0

Undeclared wars[edit]

Military engagements authorized by Congress[edit]

In other instances, the United States has engaged in extended military combat that was authorized by Congress.

War or conflict Opponent(s) Initial authorization Votes President Result
Senate House
Quasi-War France An Act further to protect the commerce of the United States
July 9, 1798
18–4 John Adams Treaty of Mortefontaine
First Barbary War Morocco Morocco


February 6, 1802[13] Thomas Jefferson War ended 1805
Second Barbary War Fictitious Ottoman flag 2.svg Algiers May 10, 1815[14] James Madison War ended 1816
Enforcing 1808 slave trade ban; naval squadron sent to African waters to apprehend illegal slave traders Slave traders and pirates "Act in addition to the acts prohibiting the Slave Trade" 1819 James Monroe 1822 first African-American settlement founded in Liberia, 1823 U.S. Navy stops anti-trafficking patrols
Redress for attack on U.S. Navy's USS Water Witch  Paraguay 1858.[15] James Buchanan
Mexican Revolution  Mexico H.J.R. 251, 38 Stat. 770
April 22, 1914
337–37 Woodrow Wilson Force withdrawn after six months. However, the Joint Resolution was likely used to authorize the Pancho Villa Expedition. In the Senate, "when word reached the Senate that the invasion had gone forward before the use-of-force resolution had been approved, Republicans reacted angrily" saying it was a violation of the Constitution, but eventually after the action had already started, a resolution was passed after the action to "justify" it since Senators did not think it was a declaration of war.[16][17]
Russian Civil War

Commune of Estonia
Far Eastern Republic
Mongolian People's Party

1918[18] Woodrow Wilson
Lebanon crisis of 1958 Lebanon Lebanese Opposition H.J. Res. 117, Public Law 85-7, Joint Resolution "To promote peace and stability in the Middle East", March 9, 1957[19] 72–19 355–61 Dwight D. Eisenhower U.S. forces withdrawn, October 25, 1958
Vietnam War

Laotian Civil War

Cambodian Civil War

China China
National United Front of Kampuchea

 North Korea
North Vietnam
Laos Pathet Lao
South Vietnam

Gulf of Tonkin Resolution, August 7, 1964 88–2 416–0 Lyndon B. Johnson U.S. forces withdrawn under terms of the Paris Peace Accords signed January 27, 1973
Multinational Force in Lebanon Shia and Druze militias; Syria S.J.Res. 159
Pub.L. 98–119
September 29, 1983
54–46 253–156 Ronald W. Reagan Forces withdrawn in 1984
Persian Gulf War Iraq H.J.Res. 77
January 12, 1991.
52–47 250–183 George H.W. Bush The United Nations Security Council drew up terms for the cease-fire, April 3, 1991
War in Afghanistan

al-Qaeda insurgency in Yemen

Somali Civil War

War in North-West Pakistan

Moro conflict

Iraqi Civil War

Syrian Civil War

Second Libyan Civil War

Afghanistan Afghanistan


Harakat Ahrar al-Sham al-Islamiyya
Hezb-e Islami Gulbuddin
Islamic Jihad Union
Islamic Movement of Uzbekistan
Turkistan Islamic Party
Tehrik-i-Taliban Pakistan

Afghanistan High Council of the Islamic Emirate
Fidai Mahaz

al-Itihaad al-Islamiya
Alliance for the Re-liberation of Somalia
Harakat al-Shabaab Mujahedeen
Hizbul Islam
Islamic Courts Union
Jabhatul Islamiya
Mu'askar Anole
Ras Kamboni Brigades

Islamic State of Iraq and the Levant Abu Sayyaf
Islamic State of Iraq and the Levant Bangsamoro Islamic Freedom Fighters
Islamic State
Islamic Movement of Uzbekistan
Islamic State of Iraq and the Levant Maute group
Islamic State of Iraq and the Levant Khalifa Islamiyah Mindanao

S.J. Res. 23
September 14, 2001
98–0 420–1 George W. Bush
Iraq War[20] Iraq H.J. Res. 114,
March 3, 2003
77–23 296–132 George W. Bush Ba'athist Iraqi government deposed April 2003. U.S. combat operations ended August 31, 2010. War ended December 15, 2011. Destabilization of Iraq and emergence of ISIL in the region 2011–present.[21]

Military engagements authorized by United Nations Security Council Resolutions and funded by Congress[edit]

In many instances, the United States has engaged in extended military engagements that were authorized by United Nations Security Council Resolutions and funded by appropriations from Congress.

Military engagement Opponent(s) Initial authorization President Result
Korean War  China

 North Korea
 Soviet Union

UNSCR 84, 1950 Harry S. Truman Korean Armistice Agreement,[22] 1953
Multinational Force in Lebanon Shia militias, Druze militias, Syria UNSCR 425, 1978

UNSCR 426, 1978

Jimmy Carter, Ronald Reagan U.S. forces withdrew in 1984
Persian Gulf War Iraq UNSCR 678, 1990 George H. W. Bush UNSCR 689, 1991
Bosnian War Republika Srpska UNSCR 770, 1992
UNSCR 776, 1992
UNSCR 836, 1993
Bill Clinton Reflagged as IFOR in 1995, Reflagged as SFOR in 1996, Completed in 2004
Second Liberian Civil War Peacekeeping UNSCR 1497, 2003 George W. Bush U.S. forces are withdrawn in 2003 after the UNMIL is established.
Haitian coup d'état UNSCR 1529, 2004

UNSCR 1542, 2004

First Libyan Civil War Libya UNSCR 1973, 2011 Barack Obama Debellation of the Libyan Arab Jamahiriya, October 31, 2011

Other undeclared wars[edit]

Military engagement Opponent(s) President Result
American Revolutionary War Kingdom of Great Britain Great Britain

German auxiliaries

Native Americans[23]

None Peace of Paris

On at least 125 occasions, the President has acted without prior express military authorization from Congress.[24] These include instances in which the United States fought in the Philippine–American War from 1898–1903, in Nicaragua in 1927, as well as the NATO bombing campaign of Yugoslavia in 1999, and the 2017 missile strikes on Syria.

The United States' longest war was fought between approximately 1840 and 1886 against the Apache Nation. During that entire 46-year period, there was never more than 90 days of peace.[citation needed]

The Indian Wars comprise at least 28 conflicts and engagements. These localized conflicts, with Native Americans, began with European colonists coming to North America, long before the establishment of the United States. For the purpose of this discussion, the Indian Wars are defined as conflicts with the United States of America. They begin as one front in the American Revolutionary War in 1775 and had concluded by 1918. The United States Army still maintains a campaign streamer for Pine Ridge 1890–1891 despite opposition from certain Native American groups.[25]

The American Civil War was not an international conflict under the laws of war, because the Confederate States of America was not a government that had been granted full diplomatic recognition as a sovereign nation by other sovereign states.[26][27] The CSA was recognized by the United States government as a belligerent power, a different status of recognition that authorized Confederate warships to visit non-U.S. ports. This recognition of the CSA's status as a belligerent power did not impose any duty upon the United States to recognize the sovereignty of the Confederacy, and the United States never did so.[citation needed]

The War Powers Resolution[edit]

In 1973, following the withdrawal of most American troops from the Vietnam War, a debate emerged about the extent of presidential power in deploying troops without a declaration of war. A compromise in the debate was reached with the War Powers Resolution. This act clearly defined how many soldiers could be deployed by the President of the United States and for how long. It also required formal reports by the President to Congress regarding the status of such deployments, and limited the total amount of time that American forces could be deployed without a formal declaration of war.

Although the constitutionality of the act has never been tested, it is usually followed, most notably during the Grenada Conflict, the Panamanian Conflict, the Somalia Conflict, the Persian Gulf War, and the Iraq War[clarification needed]. The only exception was President Clinton's use of U.S. troops in the 78-day NATO air campaign against Yugoslavia during the Kosovo War.[citation needed] In all other cases, the President asserted the constitutional authority to commit troops without the necessity of Congressional approval, but in each case the President received Congressional authorization that satisfied the provisions of the War Powers Act.

On March 21, 2011, a number of lawmakers expressed concern that the decision of President Barack Obama to order the U.S. military to join in attacks of Libyan air defenses and government forces exceeded his constitutional authority because the decision to authorize the attack was made without Congressional permission.[28] Obama explained his rationale in a two-page letter, stating that as commander in chief, he had constitutional authority to authorize the strikes, which would be limited in scope and duration, and necessary to prevent a humanitarian disaster in Libya.

See also[edit]


  1. ^ "Doe v. Bush, 03-1266, (March 13, 2003)". FindLaw. Retrieved 20 June 2013. 
  2. ^ Cooke, Alistair, Alistair Cooke's America, Alfred A. Knopf, New York, 1973.
  3. ^ Henderson, Phillip G. (2000). The presidency then and now. Rowman & Littlefield. p. 51. ISBN 978-0-8476-9739-7. 
  4. ^ The Debates in the Federal Convention of 1787 reported by James Madison : August 17,The Avalon Project, Yale Law School, retrieved Feb 13, 2008
  5. ^ "Petition for a Constitutional Amendment to Hold National Referendums on Declarations of War from Danville, Ohio". The National Archives of the United States. 1938. Retrieved July 29, 2016. 
  6. ^ Shindler, Michael (1 March 2018). "War Powers: Return to Congress". RealClearDefense. RealClear Media Group. Retrieved 2 March 2018. 
  7. ^ Official Declarations of War by Congress
  8. ^ BBC News, On This Day
  9. ^ Whereas the Government of Germany has formally declared war against the government and the people of the United States of America... the state of war between the United States and the Government of Germany which has thus been thrust upon the United States is hereby formally declared. The War Resolution
  10. ^ United States Congress (May 13, 1846). "An Act providing for the Prosecution of the existing War between the United States and the Republic of Mexico" (PDF). Government of the United States of America. Government of the United States of America. Archived from the original (PDF) on August 10, 2006. Retrieved August 10, 2006. 
  11. ^ a b c Declarations of War and Authorizations for the Use of Military Force: Historical Background and Legal Implications
  12. ^ H.J.Res.169: Declaration of War with Austria-Hungary, WWI, United States Senate
  13. ^ Key Events in the Presidency of Thomas Jefferson, Miller Center of Public Affairs, University of Virginia, (retrieved on August 10, 2010).
  14. ^ Key Events in the Presidency of James Madison, Miller Center of Public Affairs, University of Virginia, (retrieved on August 10, 2010).
  15. ^ Expenses - Paraguay Expedition, House of Representatives, 36th Congress, 1st Session, Mis. Doc. No. 86 (May 11, 1860), p. 142
  16. ^ Cyrulik, John M., A Strategic Examination of the Punitive Expedition into Mexico, 1916-1917. Fort Leavenworth, KS, 2003. (Master's thesis)
  17. ^ Wolfensberger, Don. Congress and Woodrow Wilson's Introductory Forays into Mexico, an Introductory Essay. Congress Project Seminar On Congress and U.S. Military Interventions Abroad. Woodrow Wilson International Center for Scholars. Monday, May 17, 2004
  18. ^ A History of Russia, 7th Edition, Nichlas V. Riasanovsky & Mark D. Steinberg, Oxford University Press, 2005.
  19. ^
  20. ^ Obama's full speech: Operation Iraqi Freedom is Over, MSNBC
  21. ^ Londoño, Ernesto (August 19, 2010). "Operation Iraqi Freedom ends as last combat soldiers leave Baghdad". The Washington Post. 
  22. ^ s:Korean Armistice Agreement
  23. ^ Onondaga, Mohawk, Cayuga, Seneca, Mi'kmaq (from 1779), Cherokee, Odawa, Muscogee, Susquehannock, Shawnee
  24. ^ The President's Constitutional Authority To Conduct Military Operations Against Terrorists and Nations Supporting Them
  25. ^ Army Continues to Parade Wounded Knee Battle Streamer, National Congress of American Indians.
  26. ^ "Preventing Diplomatic Recognition of the Confederacy, 1861–1865". U.S. Department of State. Archived from the original on August 28, 2013. 
  27. ^ McPherson, James M. (2007). This Mighty Scourge: Perspectives on the Civil War. Oxford University Press US. p. 65. ISBN 978-0-19-531366-6. 
  28. ^ Obama Attacked for No Congressional Consent on Libya, New York Times.

Further reading[edit]

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