Declaration of war by the United States - wikipedia Declaration of war by the United States 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. '' 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. Contents 1 History 2 Declarations of war 2.1 Formal 3 Undeclared wars 3.1 Military engagements authorized by Congress 3.2 Military engagements authorized by United Nations Security Council Resolutions and funded by Congress 3.3 Other undeclared wars 4 The War Powers Resolution 5 See also 6 References 7 Further reading 8 External links History 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. 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. 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. 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. Declarations of war Formal The table below lists the five wars in which the United States has formally declared war against eleven foreign nations. 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. 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. '' 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 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 Hungary 360 -- 0 Declaration of War upon Romania Romania 361 -- 0 Undeclared wars 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 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 Tripolitania February 6, 1802 Thomas Jefferson War ended 1805 Second Barbary War Algiers May 10, 1815 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. James Buchanan Mexican Revolution United States occupation of Veracruz 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. Russian Civil War Allied intervention in the Russian Civil War Commune of Estonia Far Eastern Republic Latvia Mongolian People 's Party Russia Ukraine 1918 Woodrow Wilson Lebanon crisis of 1958 Lebanese Opposition Al - Mourabitoun Lebanese Communist Party 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 72 -- 19 355 -- 61 Dwight D. Eisenhower U.S. forces withdrawn, October 25, 1958 Vietnam War Laotian Civil War Cambodian Civil War China National United Front of Kampuchea Khmer Rouge Khmer Rumdo Khmer Việt Minh North Korea North Vietnam Pathet Lao South Vietnam Việt Cộng 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 Operation Enduring Freedom -- Afghanistan Operation Freedom 's Sentinel al - Qaeda insurgency in Yemen Yemeni Civil War Somali Civil War Operation Enduring Freedom -- Horn of Africa War in North - West Pakistan Moro conflict Operation Enduring Freedom -- Philippines Iraqi Civil War Operation Inherent Resolve Syrian Civil War Operation Inherent Resolve Second Libyan Civil War Afghanistan Quetta Shura Taliban Haqqani network Mullah Dadullah Front al - Qaeda 055 Brigade Al - Nusra Front Khorasan group al - Qaeda Emirate in Yemen Aden - Abyan Islamic Army Islamic Jihad of Yemen al - Qaeda in the Arabian Peninsula Ansar al - Sharia al - Qaeda in the Indian Subcontinent Lashkar al - Zil Harakat Ahrar al - Sham al - Islamiyya Hezb - e Islami Gulbuddin Islamic Jihad Union Islamic Movement of Uzbekistan Jamaat - ul - Ahrar Jundallah Lashkar - e-Islam Lashkar - e-Jhangvi Tehreek - e-Nafaz - e-Shariat - e-Mohammadi Turkistan Islamic Party Tehrik - i - Taliban Pakistan 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 Abu Sayyaf Bangsamoro Islamic Freedom Fighters Islamic State Islamic Movement of Uzbekistan Maute group Khalifa Islamiyah Mindanao S.J. Res. 23 September 14, 2001 98 -- 0 420 -- 1 George W. Bush Iraq War 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. 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 Result Korean War China North Korea Soviet Union UNSCR 84, 1950 Harry S. Truman Korean Armistice Agreement, 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 2011 military intervention in Libya Operation Odyssey Dawn Operation Unified Protector Libya UNSCR 1973, 2011 Barack Obama Debellation of the Libyan Arab Jamahiriya, October 31, 2011 Other undeclared wars Military engagement Opponent ( s ) President Result American Revolutionary War Great Britain Quebec Loyalists German auxiliaries Hesse - Kassel Hesse - Hanau Hanover Waldeck Brunswick Ansbach Anhalt - Zerbst Native Americans Iroquois Confederacy None Peace of Paris On at least 125 occasions, the President has acted without prior express military authorization from Congress. 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. 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. 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. 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 Main article : 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 Persian 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. 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. 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 United States portal War portal Cold War Declaration of war by Canada Declaration of war by the United Kingdom Just War Theory Police action Timeline of United States military operations War on Terror War on Drugs References Jump up ^ `` Doe v. Bush, 03 - 1266, ( March 13, 2003 ) ''. FindLaw. Retrieved 20 June 2013. Jump up ^ Henderson, Phillip G. ( 2000 ). The presidency then and now. Rowman & Littlefield. p. 51. ISBN 978 - 0 - 8476 - 9739 - 7. Jump up ^ The Debates in the Federal Convention of 1787 reported by James Madison : August 17, The Avalon Project, Yale Law School, retrieved Feb 13, 2008 Jump up ^ `` 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. Jump up ^ Official Declarations of War by Congress Jump up ^ BBC News, On This Day Jump up ^ 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 Jump up ^ 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. ^ Jump up to : Declarations of War and Authorizations for the Use of Military Force : Historical Background and Legal Implications Jump up ^ H.J. Res. 169 : Declaration of War with Austria - Hungary, WWI, United States Senate Jump up ^ Key Events in the Presidency of Thomas Jefferson, Miller Center of Public Affairs, University of Virginia, ( retrieved on August 10, 2010 ). Jump up ^ Key Events in the Presidency of James Madison, Miller Center of Public Affairs, University of Virginia, ( retrieved on August 10, 2010 ). Jump up ^ Expenses - Paraguay Expedition, House of Representatives, 36th Congress, 1st Session, Mis. Doc. No. 86 ( May 11, 1860 ), p. 142 Jump up ^ Cyrulik, John M., A Strategic Examination of the Punitive Expedition into Mexico, 1916 - 1917. Fort Leavenworth, KS, 2003. ( Master 's thesis ) Jump up ^ 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 Jump up ^ A History of Russia, 7th Edition, Nichlas V. Riasanovsky & Mark D. Steinberg, Oxford University Press, 2005. Jump up ^ http://www.shafr.org/wp-content/uploads/2011/11/U.S.-Congress-Approval-of-the-Eisenhower-Doctrine-1957.pdf Jump up ^ Obama 's full speech : Operation Iraqi Freedom is Over, MSNBC Jump up ^ Londoño, Ernesto ( August 19, 2010 ). `` Operation Iraqi Freedom ends as last combat soldiers leave Baghdad ''. The Washington Post. Jump up ^ s : Korean Armistice Agreement Jump up ^ Onondaga, Mohawk, Cayuga, Seneca, Mi'kmaq ( from 1779 ), Cherokee, Odawa, Muscogee, Susquehannock, Shawnee Jump up ^ The President 's Constitutional Authority To Conduct Military Operations Against Terrorists and Nations Supporting Them Jump up ^ Army Continues to Parade Wounded Knee Battle Streamer, National Congress of American Indians. Jump up ^ `` Preventing Diplomatic Recognition of the Confederacy, 1861 -- 1865 ''. U.S. Department of State. Archived from the original on August 28, 2013. Jump up ^ McPherson, James M. ( 2007 ). This Mighty Scourge : Perspectives on the Civil War. Oxford University Press US. p. 65. ISBN 978 - 0 - 19 - 531366 - 6. Jump up ^ Obama Attacked for No Congressional Consent on Libya, New York Times. Further reading Grotius, Hugo ( 2004 ). On The Law Of War And Peace. Kessinger Publishing. ISBN 978 - 1 - 4191 - 3875 - 1. Edwin Meese ; Matthew Spalding ; David F. Forte ( 2005 ). The Heritage guide to the Constitution. Regnery Publishing. ISBN 978 - 1 - 59698 - 001 - 3. Kenneth A. Schultz, Tying Hands and Washing Hands : The U.S. Congress and Multilateral Humanitarian Intervention, Ch. 4, pp 105 -- 142, in Daniel Drezner, Ed. Locating the Proper Authorities : The Interaction of Domestic and International Institutions, University of Michigan Press, 2003. External links The House of Rep, Republican Study Committee of War and Military Authorized Conflicts. 2003. Declarations of war and votes Text of Declaration of War on Japan Text of Declaration of War on Germany Text of Declaration of War on Bulgaria Authorization for Use of Military Force -- signed September 18, 2001 House Joint Resolution Authorizing Use of Force Against Iraq -- signed October 16, 2002 Instances of Use of United States Forces Abroad, 1798 -- 1993 A partial list of U.S. military interventions from 1890 to 2006 U.S. - Africa Chronology Retrieved from `` https://en.wikipedia.org/w/index.php?title=Declaration_of_war_by_the_United_States&oldid=819736652 '' Categories : Wars involving the United States United States military law United States defense policymaking Declarations of war by the United States Article One of the United States Constitution Hidden categories : Use mdy dates from December 2011 All articles with unsourced statements Articles with unsourced statements from June 2010 Wikipedia articles needing clarification from August 2015 Articles with unsourced statements from March 2008 Talk Contents About Wikipedia Português Edit links This page was last edited on 11 January 2018, at 00 : 36. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: when was the last time the us formally declared war
Answer: June 5, 1942