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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.


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. Many have postulated "Declaration(s) of War" must contain that phrase as or within the title. Others oppose that reasoning. In the courts, the United States First Circuit Court of Appeals 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.

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.[2] 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.[3] Debate continues as to the legal extent of the President's authority in this regard.

After Congress repealed the Gulf of Tonkin Resolution in January 1971 and President Richard Nixon continued to wage war in Vietnam, Congress passed the War Powers Resolution (Pub.L.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.

Declarations of war[]


The table below lists the five wars in which the United States has formally declared war against eleven foreign nations.[4] 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.[5][6]

War Declaration Opponent(s) Date of declaration Votes President Conclusion
Senate House
War of 1812 Declaration of War upon the UK  United Kingdom of Great Britain and Ireland June 18, 1812 19–13 79–49 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."[7]  Mexico May 13, 1846 40–2 173–14 Polk Treaty of Guadalupe Hidalgo (February 2, 1848)
Spanish-American War Declaration of War upon Spain  Spain April 25, 1898 42–35 310–6 McKinley Treaty of Paris (December 10, 1898)
World War I Declaration of War upon Germany (1917)  German Empire April 6, 1917 82–6 373–50 Wilson Treaty of Berlin (August 25, 1921)
Declaration of War upon Austria-Hungary [1]  Austria-Hungary December 7, 1917 74–0 365–1 Treaty of Trianon (in part)
World War II Declaration of War upon Japan  Empire of Japan December 8, 1941 82–0 388–1 Roosevelt,
V-J Day, Japanese Instrument of Surrender (September 2, 1945), Treaty of San Francisco (September 8, 1951)
Declaration of War upon Germany (1941)  Nazi Germany December 11, 1941 88–0 393–0 V-E Day, Unconditional German 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  Kingdom of Italy 90–0 399–0 Paris Peace Treaty (February 10, 1947)
Declaration of War upon Bulgaria  Kingdom of Bulgaria June 5, 1942 73–0 357–0
Declaration of War upon Hungary [2]  Kingdom of Hungary (1920–46) 360–0
Declaration of War upon Romania [3]  Kingdom of Romania 361-0

Military engagements authorized by Congress[]

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 Conclusion
Senate House
Quasi-War  France Act Further to Protect the Commerce of the United States
July 9, 1798
Adams Convention of 1800 (Treaty of Mortefontaine)
First Barbary War Tripoli February 6, 1802[8] Jefferson 1805
Second Barbary War Algiers May 10, 1815[9] Madison 1816
enforcing 1808 slave trade ban; naval squadron sent to African waters to apprehend illegal slave traders slave traders (pirates) "Act in addition to the acts prohibiting the Slave Trade" 1819 Monroe 1822 first African-American settlement founded in Liberia, 1823 US Navy stops anti-trafficking patrols
Redress for attack on U.S. Navy vessel  Paraguay 1859.[10] Buchanan
United States occupation of Veracruz  Mexico H.J.R. 251, 38 Stat. 770
April 22, 1914
337-37 Wilson Force withdrew after six months. However, the Joint Resolution was likely used to authorize the Punitive Expedition against Pancho Villa. 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.[11][12]
Intervention during the Russian Civil War  Russia 1918 [13] Wilson
Lebanon crisis of 1958 Lebanese opposition, led by
23x15px Al-Mourabitoun
Progressive Socialist Party
H.J. Res. 117, Public Law 85-7, Joint Resolution "To promote peace and stability in the Middle East", March 9, 1957 [14] 72-19 355-61 Eisenhower U.S. forces withdrawn, Oct. 25, 1958
Vietnam War Viet Cong
 North Vietnam
Gulf of Tonkin Resolution, August 7, 1964 88–2 416–0 Kennedy


U.S. forces withdrawn under terms of the Paris Peace Accords signed Jan. 27, 1973
Multinational Force in Lebanon Shia and Druze militias; Syria S.J.R. 159
September 29, 1983
54–46 253–156 Reagan Force withdrew in 1984
Gulf War, also known as Operation Desert Storm  Iraq H.R.J. Res. 77
January 12, 1991.
52–47 250–183 GHW Bush The United Nations Security Council drew up terms for the cease-fire, April 3, 1991
2001 war in Afghanistan, also known as Operation Enduring Freedom 23x15px Afghanistan
S.J. Res. 23
September 14, 2001
98–0 420–1 George W. Bush
Barack Obama
Iraq War, also known as Operation Iraqi Freedom, currently known as "Operation New Dawn."[15]  Iraq H.J. Res. 114,
March 3, 2003
77–23 296–133 George W. Bush
Barack Obama
Combat operations ended August 31, 2010. Officially ended December 15, 2011.[16]

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

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 Conclusion
Korean War  North Korea

 People's Republic of China

UNSCR 84, 1950 Harry S. Truman Armistice[17] 1953
Multinational Force in Lebanon Shia militia,

Druze miltia, Syria

UNSCR 425, 1978

UNSCR 426, 1978

Jimmy Carter

Ronald Reagan

US forces withdrew in 1984
Gulf War,

also known as Operation Desert Storm

 Iraq UNSCR 678, 1990 George H. W. Bush UNSCR 689, 1991
Bosnian War

also known as UNPROFOR

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 US Forces withdraw in 2003 after UNMIL is established
2004 Haitian coup d'état,

also known as MINUSTAH

UNSCR 1529, 2004

UNSCR 1542, 2004

2011 Military Intervention in Libya

also known as Operation Odyssey Dawn

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

Other undeclared wars[]

On at least 125 occasions, the President has acted without prior express military authorization from Congress.[18] 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.

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.[19]

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.[20][21] 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.

The War Powers Resolution[]

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 Gulf War, and the Iraq War. 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 was made to authorize the attack without Congressional permission.[22]

See also[]


  1. "Doe v. Bush, 03-1266, (March 13, 2003)". FindLaw. Retrieved 20 June 2013. 
  2. Henderson, Phillip G. (2000). The presidency then and now. Rowman & Littlefield. p. 51. ISBN 978-0-8476-9739-7. 
  3. The Debates in the Federal Convention of 1787 reported by James Madison : August 17,The Avalon Project, Yale Law School, retrieved Feb 13, 2008
  4. Official Declarations of War by Congress
  5. BBC News, On This Day
  6. 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
  8. Key Events in the Presidency of Thomas Jefferson, Miller Center of Public Affairs, University of Virginia, (retrieved on August 10, 2010).
  9. Key Events in the Presidency of James Madison, Miller Center of Public Affairs, University of Virginia, (retrieved on August 10, 2010).
  10. Expenses - Paraguay Expedition, House of Representatives, 36th Congress, 1st Session, Mis. Doc. No. 86 (May 11, 1860), p. 142
  13. A History of Russia, 7th Edition, Nichlas V. Riasanovsky & Mark D. Steinberg, Oxford University Press, 2005.
  16. Londoño, Ernesto (August 19, 2010). "Operation Iraqi Freedom ends as last combat soldiers leave Baghdad". The Washington Post. 
  17. s:Korean Armistice Agreement
  18. The President's Constitutional Authority To Conduct Military Operations Against Terrorists and Nations Supporting Them
  19. Army Continues to Parade Wounded Knee Battle Streamer, National Congress of American Indians.
  20. "Preventing Diplomatic Recognition of the Confederacy, 1861–1865". U.S. Department of State. 
  21. McPherson, James M. (2007). This mighty scourge: perspectives on the Civil War. Oxford University Press US. p. 65. ISBN 978-0-19-531366-6. 
  22. Obama Attacked for No Congressional Consent on Libya, New York Times.

Further reading[]

External links[]

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