The U.S. enters the war in Europe Pres. Franklin D. Roosevelt signing the declaration of war against Germany while Sen. Tom Connally (standing, right) marks the time of the signature with his pocket watch, December 11, 1941. (more) How Many Times Has the United States Declared War? Written by Michael Ray Michael Ray is an assistant managing editor who has worked at Britannica since 2003. In addition to leading the Geography and History team, he oversees coverage of European history and military affairs.... Michael Ray Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Mar. 6, 2026 •History 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 the declarations of war against the minor Axis powers of Bulgaria, Hungary, and Romania....

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