In the United States and other countries around the world, a formal or official declaration of war is not taken lightly. The writers of the Constitution of the United States of America assigned the ability to declare war when they described the powers of each branch of government in the document.

Where the Power Lies

In the United States, the power to declare war and appropriate military funds lies with the legislative branch of government, but the executive branch supplies the commander in chief of the military, capable of some military actions even without an official declaration of war. The first official declaration of war Congress made was against Great Britain in 1812, while the most recent declarations of war took place during World War II.

On Paper

Article I, Section 8, Clause 11 of the Constitution assigns the power to declare war to Congress, stating that the power rests with Congress: "To declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water; To raise and support armies ... To provide for calling for the militia to execute the laws of the union, suppress insurrections and repel invasions." Article II, Section 2 of the constitution says that "The President shall be commander in chief of the Army and Navy of the United States and the militia of the several states, when called into the actual service of the United States."