During the Vietnam war the Mobile Riverine Force used LCM-6 Mod-0 and Mod-1 vessels converted into specialized fighting river craft designated as ATC. The craft had crew quarters built into part of the well deck and were fitted with sponsons. Three armored gun turrets revolved and sides were covered with 1" rebar intended to take the impact of exploding RPG rounds. Often ration boxes were placed between the rebar and inner plate armor to absorb shrapnel.
All "normal" ATCs were Program IV and were dedicated Armored Troop Carriers that moved troops of the US Ninth Infantry Division into combat with the enemy.
A few Program IV ATCs were further modified:
ATC-H had a helicopter deck installed above the well deck capable of landing a UH-1 Huey for MedEvac purposes.
ATC-R same as ATC-H with an added diesel fuel bladder in the well deck to refuel other ATCs or Hueys.
Program V ATC's were converted from LCM-6 Mod-2 craft which included Zippo Boats, 40mm Monitors and 105mm Monitors. Additionally there were 2 boats that had powerful water cannon machinery installed (ATC-WC) in the well deck which was used to hydraulically destroy enemy tunnels dug into the river banks. The first (Tango-14) was a Program IV craft and a follow on (Tango-32) a Program V.
"Irma La Douche"
Tango-14 was commanded by BM-1 Ray F. Longaker Jr. from 10/1969 to 10/1970 and operated on the rivers south of Saigon and west to the Cambodian border together with Tango 32. "The boat was a big slow target and going against the current with a flat bow ramp the top speed was maybe 4 knots. When in a fire fight we were in the kill zone a long time and had to fight our way out. Long time meaning melting the barrels off the machine guns. We were in a number of fire fights and its a wonder why nothing - including us - was hit." In the one year Tango-14 destroyed over 370 bunkers, spider-holes, trenches and booby traps, plus the capture of two significant enemy ammunition cashes.