Refers to a facility where military personnel are stationed and operations are conducted.
There is an American military base on that island.
The area around the military base is off-limits.
基地 is a general term for 'base' (military, research, etc.), while 軍事基地 specifically means 'military base'.
駐屯地 refers to a garrison or station for troops, often a smaller or more specific military post.
Compound of 軍事 (military affairs) and 基地 (base).