On July 20, 1973, the War Powers Resolution was passed as a joint resolution of Congress. The resolution provides that the President can send armed forces into action abroad only by authorization of Congress or if the United States is already under attack or serious threat.

Under the United States Constitution, war powers are divided between Congress and the President. Congress has the power to declare war, raise and support the armed forces, control the war funding, and make laws necessary for war. The President is commander-in-chief of the armed forces, giving the President power to repel attacks against the United States and lead the armed forces. Further, the President has the right to sign or veto congressional acts, such as a declaration of war.

The War Powers Resolution was proposed because the Korean and Vietnam wars saw the United States involved in situations of intense conflict without an official declaration of war. Members of Congress were concerned that Congress was losing the authority to decide when the United States should become involved in a war. The War Powers Resolution was passed by both the House of Representatives and Senate on July 20, 1973. However, the resolution was vetoed by President Richard Nixon. Congress overrode the veto by a two-thirds majority vote in each house and enacted the joint resolution into law.

The War Powers Resolution requires the president to notify Congress within 48 hours of committing armed forces to military action. The Resolution also forbids armed forces from remaining in an occupied area for more than 60 days without an authorization of the use of military force or a declaration of war.