Army: The United States Army is the largest branch of the armed forces and is responsible for land-based military operations. The modern army has its roots in the Continental Army which was formed June 14th 1775 to meet the demands of the American Revolutionary War before the establishment of the United States. The Army's mission is to fight and win our Nation's wars by providing prompt, sustained land dominance across the full range of military operations. The army motto is "This We'll Defend."