Tunnel rat The tunnel rats were American , Australian and New Zealand soldiers who performed underground search and destroy missions during the Vietnam War . Later , similar teams were used by the Soviet Army during the Soviet war in Afghanistan . Vietnam War . During the Vietnam War " tunnel rat " became a more or less official speciality for volunteer infantrymen , primarily from the United States , Australia , and New Zealand . Their motto was the Latin phrase " Non Gratum Anus Rodentum " - " Not worth a rat ' s ring " . Since the 1940s , during the war against the French colonial forces , the Viet Cong had created an extensive underground system of complexes . By the 1960s there were underground hospitals , training grounds , storage facilities , headquarters , and more . The Viet Cong , who were crack forces highly skilled at guerilla warfare , might stay underground for several months at a time . The tunnels were their territory . Whenever troops would uncover a tunnel , tunnel rats were sent in to kill any hiding enemy soldiers and to plant explosives to destroy the tunnels . A tunnel rat was equipped with only a standard issue . 45 caliber pistol , a bayonet and a flashlight , although most tunnel rats were allowed to choose another pistol with which to arm themselves . The tunnels were very dangerous , with numerous booby trap s and enemies lying in wait . Often there were flooded U - bends in the tunnels to trap poison gas . Underground , gas could be a very deadly weapon , and a tunnel rat might choose to go into the tunnels wearing a gasmask as it would be impossible to put one on in a narrow tunnel . But more often than not , a tunnel rat would take his chances without a gasmask , as it made even harder to see , hear , and breathe in the narrow , dark tunnels . The tunnels presented many potential threats ; enemy soldiers manned holes on the sides of tunnels through which spears could be thrust , impaling a crawling intruder . Not only were there human enemies , but also dangerous creatures , such as snakes ( including venomous ones - sometimes placed there as living booby traps ) , rats , spiders , scorpions , and ant s . Black - Bearded Tomb Bat s ( " Taphozous melanopogon " ) and Lesser Dawn Bat s ( " Eonycteris spelaea " ) also roosted in the tunnels , though they were a harmless nuisance if awakened . Due to the confined space , the tunnel rats disliked the intense muzzle blast of the comparatively large . 45 caliber round , which would often leave them temporarily deaf , and it was not uncommon for them to use whatever handgun they might find . The Soviet - made pistols the enemy carried were particular favorites , but they were rare , and the soldiers would often have someone at home send them a civilian pistol or revolver . Among the favorites were the smaller German Luger or less - common double action Walther pistols , both chambered in 9 mm . Many of these were brought home by American troops returning from World War II . Others would trade their pistols for revolvers used by other personnel . Many used improvised suppressor s on their pistols to further reduce the noise . A particularly favored weapon was a specially modified Smith & Wesson Model 29 known as the " quiet special purpose revolver " . Unlike the standard Model 29 , which fires a . 44 Magnum cartridge , the quiet special purpose revolver instead shot a specially designed quiet captive - piston cartridge sized as a . 410 shotgun shell . The cartridge resembles later Soviet efforts such as those used in the OTs - 38 revolver In addition , that made the revolver lighter and more useful in a tight , confined space . Tunnel rats were generally , but not exclusively , men of smaller stature ( 5 ' 6 and under ) in order to fit in the narrow tunnels . Mangold and Penycate claimed that the tunnel rats were almost exclusively White or Hispanic soldiers , and the majority of American Latinos were Puerto Rican or Mexican American . Such tactics came to prominence following their successful application in January 1966 during a combined US - Australian action against the Củ Chi tunnels in Binh Duong Province , known as Operation Crimp . Afghanistan . Afghanistan has an extensive series of historic tunnels used for transporting water , the " kariz " , and during the 1979 – 1989 Soviet war in Afghanistan , such tunnels were used by Mujahideen fighters . The Soviet 40th Army had their own tunnel rats , who were tasked with flushing people out of the tunnels , then going through the tunnels to disarm booby traps and kill those who remained . The United States Marine Corps and the Royal Marines are involved in similar work during the current ongoing war in Afghanistan .