Stage 3 - Vietnam - Tunnel Rat
There was potentially no more terrifying a combat task during the Vietnam conflict than that of being the tunnel rat. The VC and NVA created extensive underground systems to avoid the systematic and massive US bombing campaigns, not only to survive, but also to hide food, weapons and men. These tunnel systems were frequently multiple levels deep with many entrances and exits. These tunnels afforded guerilla hit-and-run tactics in which they could hit US forces, enter the tunnel and exit somewhere else entirely, or merely wait in well hidden entrances to ambush unsuspecting US forces.
US "tunnel rats" would strip down to sometimes nothing more than pants, a belt, a flashlight and a gun to fit into these claustrophobic subterranean horrors and engage in closer than close CQB, alone and without backup.