National Guard

In the U.S., state-by-state reserve army units. Technically under the command of a state governor, but can be activated as part of the U.S. Army when needed. Some Guard units go on active duty fairly often, because they may have strengths in particular military occupation specialties that are rare in the regular Army.

In the United States, the organized militia forces of the individual states, that is is trained, and has its officers appointed, by the States according to the discipline prescribed by Congress*; is organized, armed, and equipped wholly or partly at Federal expense; and is federally recognized. It is a component of the Army of the United States when called into active federal service. The National Guard consists of the Army National Guard and the Air National Guard.

* - U.S. Constitution, article I, section 8, clause sixteen