Battery (military unit)
A battery is the traditional basic sub-unit of artillery formations. The most basic is the firing battery, which contains some number of cannon, multiple rocket launchers, or guided missile launchers that will fire together; there are typically 4-8 such pieces. It is usually commanded by a captain.
Other batteries may carry out specialized artillery functions such as target acquisition, ammunition supply, and maintenance. There is apt to be a headquarters battery in an artillery battalion.
Batteries may be assigned in direct support of a maneuver unit (e.g., infantry or armor). In such cases, they will depend on the supported unit for supply and maintenance. Otherwise, batteries in general support are usually organized as battalions.