Military history of the United States
The military history of the United States spans a period of over two centuries. During those years, the United States evolved from a new nation fighting Great Britain for independence (1775–83), through the monumental American Civil War (1861–65) and, after collaborating in triumph during World War II (1941-1945), to the world's sole remaining superpower of the late 20th century and early 21st century.The Continental Congress in 1775 established the Continental Army and named General George Washington its commander. This newly formed army, along with state militia forces, and the French army and navy, defeated the British in 1781. The new Constitution in 1789 made the president the commander in chief, with authority for the Congress to levy taxes, make the laws, and declare war.As of 2015, the U.S. military consists of an Army, Navy, Air Force and Marine Corps under the command of the United States Department of Defense. There also is the United States Coast Guard, which is controlled by the Department of Homeland Security.The President of the United States is the commander in chief, and exercises the authority through the Secretary of Defense and the Chairman of the Joint Chiefs of Staff, which supervises combat operations. Governors have control of each state's Army and Air National Guard units for limited purposes. The president has the ability to federalize National Guard units, bringing them under the sole control of the Department of Defense.