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 (1775–1783), through the monumental American Civil War (1861–1865) and, after collaborating in triumph during World War II (1941–1945), to the world's sole remaining superpower from the late 20th century to present.
The Continental Congress in 1775 established the Continental Army, Continental Navy, and Continental Marines and named General George Washington
its commander. This newly formed military, along with state militia
forces, the French Army and Navy, and the Spanish 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 2017, the U.S. Armed Forces consists of the Army, Marine Corps, Navy and Air Force, all 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.
