Prior to and during the founding of the United States, military forces were supplied by untrained militia commanded by the states. When the Continental Congress first ordered a Continental Army to be formed, it was to be made up of militia from the states. That army, under the command of General George Washington, won the Revolutionary War, but afterwards was disbanded.
However, it soon became obvious that a standing army and navy were required. The United States Navy (and the Marine Corps) began when Congress ordered several frigates in 1794, and a standing army was created, however it was still only minimal and it relied mostly on contributions from state militia in times of war. The Coast Guard was created in 1790.