The JLTV or Joint Light Tactical Vehicle was a new US military programme, initiated to partially replace the fleet of ageing HMMWV utility vehicles. The new vehicle is intended for the US Army, Marine Corps and Special Forces.
M1278 is a heavy guns carrier. It is a baseline 4-door general-purpose version of the JLTV family. It has a shielded M2 heavy machine gun station on the roof. Alternatively it can be fitted with various remotely-controlled weapon stations, armed with the M2 12.7 mm heavy machine gun, or even lightweight 30 mm chain gun.
M1279 is an utility version. It is a 2-door pickup with a cargo area at the rear. It can carry various supplies and cargo.
M1281 is a close combat weapons carrier.