The Army, Air Force, Coast Guard, Marine Corps, Navy and Space Force are the branches of armed forces of the United States. All branches have soldiers on active duty, who serve full-time, working in the United States or other countries. Each branch of the military has a reserve component, such as the Army Reserve, comprising part-time soldiers with civilian jobs who report for duty on a set schedule and may be called up to active duty.

Commissioned officers typically have earned at least a four-year degree before entering the military. Officers serve in specialized fields — typically determined by their degree(s) — and also serve in management roles.

There are many jobs within the military including medical personnel, engineers and information technology roles. Defense industry contractors provide technology, equipment and service to support the military and are considered part of this field even though they are not part of the government. 

You can do additional research on this field in the Firsthand Guide to Defense Jobs.