The U.S. Military consists of five active-duty Services and their respective Guard and Reserve units. All branches are equal parts of the United States Uniformed Services, headed by the president as commander in chief. The Army, Marine Corps, Navy and Air Force fall under the jurisdiction of the Department of Defense (DoD). The Coast Guard reports to the Department of Homeland Security during peacetime and to the DoD (by way of the Navy) during wartime.
Reserve and National Guard units perform as active-duty servicemembers on a part-time basis. These troops train close to home, deploying when needed to aid in international conflict or domestic disaster relief.