The United States Armed Forces are the overall unified military forces of the United States of America. The United States military was first formed by the second Continental Congress to defend the new nation against the British Empire in the American Revolutionary War. The Army, Marine Corps, and Navy were commissioned in 1775, in anticipation of the declaration of independence in 1776. The Coast Guard originated as the Revenue Cutter Service, which was formed in 1790. The Revenue Cutter Service merged with the United States Life-Saving Service in 1915 to become the Coast Guard. The United States Air Force originated as the United States Army Air Corps in 1926 and became an independent service in 1947.