noun
main force; main troops
Military term for the primary combat unit or the bulk of one's forces, as opposed to support or reserve units.
敵の主力部隊は山の向こうに集結している。
The enemy's main force is massing beyond the mountains.
主力部隊が到着するまで持ちこたえなければならない。
We must hold out until the main troops arrive.
Compound of 主力 (main strength) and 部隊 (military unit).