Being a tunnel rat was one of the deadliest jobs in Vietnam, and required a whole lot of courage, and a pinch of insanity. You had to be small generally, so you could fit into the small wholes that the VC had created for access to their underground fortresses. Once in, your mission was to locate any and all VC and NVA troops and neutralize them. Generally you carried a pistol and a flashlight unless the tunnel was large enough and allowed for a larger weapon such as an M16. These tunnel systems extended all over Vietnam for thousands of miles and housed many thousands of NVA and VC troops and were also used as headquarters, logistical depots, barracks, etc...