How Many Times Has the United States Declared War?

Article 1, Section 8 of the United States Constitution clearly states that “The Congress shall have Power…To declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water.” Since the adoption of the Constitution in 1789, the United States has declared war 11 times—most recently on June 5, 1942, when Pres. Franklin D. Roosevelt signed declarations of war against the minor Axis powers of Bulgaria, Hungary, and Romania.

When a war isn’t declared: Police actions, conflicts, and authorized uses of military force

This, obviously, did not mark the end of U.S. military operations. Just five years after the conclusion of World War II, the United States was a principal combatant in a “police action” on the Korean Peninsula. The absence of a congressional declaration did not make a conflict that lasted more than three years and claimed at least 2.5 million lives any less a “war.” Indeed, it reflected a trend that had already been noted prior to the ratification of the Constitution more than a century and a half earlier. In “Federalist 25” (December 1787) Alexander Hamilton observed that “the ceremony of a formal denunciation of war has of late fallen into disuse.”

U.S. presidents from the second half of the 20th century onward commonly ordered troops into harm’s way under the auspices of a congressional authorization of the use of military force (AUMF)—that is, if congressional approval was sought at all. Probably the most conspicuous examples of AUMFs are the Gulf of Tonkin Resolution (August 5, 1964), which vastly increased U.S. involvement in the Vietnam War; and the AUMF of 2001 (September 18, 2001), which passed in the days after the September 11 attacks and granted a succession of presidents wide latitude in the prosecution of the so-called “global war on terrorism.”

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On November 7, 1973, Congress passed the War Powers Act over the veto of Pres. Richard Nixon. This legislation was designed to prevent “future Vietnams” by requiring the executive branch to consult with and report to Congress before undertaking military action abroad. In reality, the War Powers Act has done little to constrain presidents from both parties in this regard.

U.S. congressional declarations of war

As illustrated by the table, congressional votes on declarations of war have traditionally been one-sided (if not unanimous). The most glaring exception to this rule was the very first declaration of war in U.S. history. New England Federalists vehemently opposed a conflict with England, while southern and western War Hawks in the Democratic-Republican Party viewed the war as a matter of restoring American honor in the face of British insults. The vote to approve what Federalists derisively called “Mr. Madison’s War” fell along strict party lines, with every vote in favor of the war coming from the Democratic-Republicans, while the Federalists were united in their opposition.

One other notable figure in the table is the single vote against a declaration of war on Japan in December 1941. It was cast by Rep. Jeannette Rankin of Montana, an avowed pacifist who was also the first woman elected to Congress. Rankin had voted against the declaration of war on Germany in 1917, and this second “no” vote effectively ended her political career. She remained opposed to war, however—declared or otherwise. On January 15, 1968, at the age of 87, she led a march of 5,000 women to the steps of the Capitol to demand an end to the Vietnam War.