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 United States 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.
The last time the United States formally declared war, using specific terminology, 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 formal declaration of war. Since then, every American president has used military force without a declaration of war.
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.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.
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|
|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 Pub.L. 77–564||Hungary||360–0|
|Declaration of War upon Romania Pub.L. 77–565||Romania||361–0|
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|
|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 ||"An Act for the Protection of the Commerce and Seamen of the United States, Against the Tripolitan Cruisers", 2 Stat. 129, February 6, 1802||Thomas Jefferson||War ended 1805|
|Second Barbary War||Algiers||"An Act for the protection of the commerce of the United States against the Algerine cruisers", 3 Stat. 230, 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", 3 Stat. 532, 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||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||1918||Woodrow Wilson|
|Lebanon crisis of 1958||Lebanese Opposition||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 ||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 |
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 on Terror|| Afghanistan |
Harakat Ahrar al-Sham al-Islamiyya
High Council of the Islamic Emirate
| 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 abolished April 2003, Saddam Hussein executed. |
War ended December 15, 2011. Destabilization of Iraq and emergence of ISIL (ISIS) in Iraq region 2014–2017.
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 ||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||Libya||UNSCR 1973, 2011||Barack Obama||Debellation of the Libyan Arab Jamahiriya, October 31, 2011|
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, against the Taliban in Afghanistan, began in 2001 and is still ongoing as of 2020 [update] .
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.
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