lone force; isolated army
Refers to a military unit or group fighting alone without support or reinforcements. Often used in the set phrase 孤軍奮闘 (fighting alone against great odds).
They became an isolated force in enemy territory.
孤軍奮闘の末、ついに援軍が到着した。
After fighting alone against great odds, reinforcements finally arrived.
fighting alone; struggling single-handedly
From 孤 (solitary, alone) + 軍 (army, force). The exact historical derivation is uncertain, but the compound is used in classical and modern Japanese to describe an unsupported military unit.