While the likes of the Willys MB (and closely related Ford GPW) and AM General HMWWV "Humvee" are generally the first vehicles that come to mind in a discussion about U.S. military vehicles, there's a long history of support vehicles that fill critical behind-the-scenes transport and logistics roles.
Below is a list of such trucks, starting from the World War II era.
The Dodge WC series was a versatile truck that came in multiple configurations for many different uses, including weapon carriers, ambulances, command cars, and reconnaissance vehicles. Some were offered in tandem rear axle 6x6 configurations. Despite weights of up to almost 7000 lb, the WC-series trucks were powered by a mere 4.0-liter inline-six with a maximum output of 99 hp and 188 lb-ft in its most powerful configuration. Production of the WC trucks ran from 1940 through the end of the war in 1945.
Following World War II, the Dodge M37 became the workhorse during the Korean War. The M37 got a reputation for engine failures as the average speed of military vehicles increased into the 1960s, largely due to the combination of the T245 flathead inline-six's extremely long stroke with the short gearing needed for hauling heavy loads at low speeds. Because of the large number of M37s produced, replacement parts and engines are relatively easy to find, and the Hercules company offers engine upgrades for retired M37s.
The Kaiser Jeep M715 is one of the most famous Jeep pickups and served as the basis of the 2010 Jeep NuKizer concept. The M715 had an advanced overhead-cam 3.8-liter inline-six engine that was a massive improvement over the L-head straight-six it replaced in terms of both power output and fuel efficiency, but gained a reputation for having poor reliability. More than 33,000 M715s were built between 1967-1969.
The Dodge M880 marked the early stages of the military's CUCV (Commercial Utility Cargo Vehicle) program. The M880 was essentially a militarized version of Dodge's third-generation D-series civilian trucks, but it proved to be an awkward fit for their intended applications. The trucks were powered by a 5.2-liter gasoline V-8 engine, but much of the armed services was moving to diesel, and they were not equipped with power steering -- this was a choice likely initially made for durability and reliability reasons, but made the trucks a bear to drive, especially in tight quarters. However, the M880 did feature front disc brakes.
The CUCV that replaced the M880 was based on GM's full-size trucks. It was powered by a 6.2-liter naturally-aspirated Detroit Diesel V-8 engine mated to a TH-400 automatic transmission. The M1008 was the basic cargo truck, with other variations being the M1010 ambulance, and the M1009, which was a K5 Blazer upgraded with three-quarter ton hardware. There were also variants that served as shelter carriers and mobile command centers.
GM CUCV II
The CUCV II is based on the GMT-400 chassis and was introduced in 1996. These were upfitted civilian trucks equipped with special hardware for military use. Among the upgrades were bumpers and front grilles outfitted with pintles and towing/loading shackles, and extra leaf springs to give them higher payload capacity. It also had a 24-volt dual battery starting system, although the rest of the vehicle retained a 12-volt system. In contrast to some of its more spartan predecessors, the CUCV II was equipped with an AM/FM radio and air conditioning.
GM CUCV III
The CUCV III was based on GM's new GMT-800 truck chassis, and was available with a brush guard, on-board air compressor, navigation system, 120-volt AC power inverter, front or rear winch, and run-flat tires. The CUCV III got a major power upgrade from the former 6.2/6.5-liter Detroit to the new 6.6-liter Duramax diesel mated to an Allison 5-speed automatic transmission. Other hardware sure to make truck enthusiasts jealous are 35-inch run-flat tires and beadlock wheels
The GM LSSV is the next-generation of support vehicle and is based on the GMT-900 HD truck chassis. Similar to the CUCV III, the LSSV is powered by the Duramax diesel V-8, available in a crew cab or standard cab configuration. It could also be equipped with an enhanced mobility package which added underbody protection, and a tire pressure monitoring system, among other features. Upfitting of the LSSV for military duty is performed by AM General, which made the original HMMWV, and its civilian counterparts, the Hummer H1 and H2.