frontline base; forward base; outpost
Military term for a base located near the front lines, used for operations and support.
The unit launched an attack from the frontline base.
Supplies to the forward base were cut off.
基地 is a general term for a base (military, research, etc.), while 前線基地 specifically refers to a base near the front lines.
前線 means 'front line' or 'front' in a military or metaphorical sense; 前線基地 is a compound meaning 'frontline base'.
Compound of 前線 (front line) and 基地 (base).