Declarations of War and AUMFs AUMF

Article I, Section 8 gives Congress the power to declare war, while Article II makes the President commander in chief. Congress has formally declared war 11 times in five conflicts: the War of 1812, the Mexican-American War in 1846, the Spanish-American War in 1898, World War I against Germany and Austria-Hungary in 1917, and World War II against Japan, Germany, Italy, Bulgaria, Hungary, and Romania in 1941 and 1942. The last declaration, against Romania, Hungary, and Bulgaria, was passed on June 4 and signed on June 5, 1942.

Since then Congress has authorized military action through statutes and joint resolutions that do not declare war, including the Gulf of Tonkin Resolution of August 1964, which presidents relied on to escalate the Vietnam War, the 1991 authorization for the Gulf War, the Authorization for Use of Military Force passed on September 18, 2001, against those responsible for the September 11 attacks, and the 2002 authorization for the Iraq War. The 2001 law, only 60 words long, has been used to justify operations against groups that did not exist in 2001 in more than a dozen countries.

Presidents of both parties have also used force without specific authorization, citing their constitutional powers, from Korea in 1950 to Libya in 2011 and strikes on Iranian nuclear sites in June 2025, and in 2025 the administration carried out strikes on boats it said were carrying drugs, arguing the country was in an armed conflict with cartels. On January 3, 2026, U.S. forces struck targets in Caracas and captured Venezuelan leader Nicolas Maduro without congressional authorization, and in January the Senate defeated a war powers resolution on the operation by a 50 to 50 vote broken by the Vice President. Congress repealed the 1991 and 2002 Iraq authorizations in the defense authorization law signed on December 18, 2025, while efforts to narrow the 2001 law continue. Supporters of broad presidential authority say modern threats require speed, while critics say Congress has abandoned its constitutional responsibility to decide when the nation goes to war.