The HEMTT platform was designed to provide heavy transport capabilities for supply and re-supply of combat vehicles and weapons systems for the United States Army. First introduced in 1985, the HEMTT replaced the M520 Goer Trucks and became nicknamed the "Dragon Wagon" based on its unique shape.

Its prominent features include extreme mobility compared to standard 5-ton trucks thanks to a large number of wheels and turbo-charged engine combined with all-wheel drive and very large low-pressure tires.

Though far less publicized than the HMMWV, the HEMTT has been an enabling force in transporting logistics behind quick-moving forces based on the M1 Abrams tank. Having proved itself as a key workhorse of the US heavy tactical wheeled vehicle fleet over 13,000 HEMTT vehicles are in service.

Since 1985, the HEMTTs have become the backbone of the US Army's logistics fleet. After 1991 the performance of the vehicles started to deteriorate. In 2001 the HEMTT Recapitalization Program was established by Oshkosh and the US Army. Under the scheme new and recapitalized vehicles were provided to many high-priority units. The recapitalization generates "like-new" vehicles with a new warranty for a cost of around 12% less than new vehicle procurement. By 2003 about 621 trucks were contracted for recapitalization.

In December 2002, the R3 (recap, repair and return) programme was developed by the US Army and Oshkosh to increase the recapitalization turnaround rate of HEMTTs.

The programme reduced the turnaround to 100 days including shipping time. After the R3 programme, the vehicles received the designation R1 on their model numbers.

In 2005 Oshkosh Corporation started developing next-generation HEMTT A3 vehicles after receiving a grant from the US Department of Defense. The vehicles passed the performance and durability tests over the following 18 months. The A3 remains a technology demonstration for a hybrid powertrain.

In February 2008, the first modification contract of the HEMTT A2s was placed by the US Army. The second modification contract designated the name of the HEMTT A2 vehicles as the HEMTT A4.

Oshkosh has produced 11 HEMTT variants in six configurations; five cargo trucks, a fuel servicing truck variant, two tractor variants, a load handling system variant, a common bridge transporter variant and a recovery vehicle with cranes and winches.

The common features of the variants include front and rear tow eyes, blackout lights, 24-volt electrical systems and rear pintle hooks for towing trailers and artillery.

HEMTTs can traverse hard terrain while transporting combat vehicles and weapons to the field. HEMTT variants are fitted with power-assisted front tandem steering systems on a wheelbase of 5.3m. Carrying a maximum payload of 13t, they can climb a 60% gradient and ford water at a depth of 1.2m. They deliver a cruising range of 644km and can be easily transported in a C-130.

The Heavy Expanded Mobility Tactical Truck Extended Service Program (HEMTT-ESP) is a Vice Chief of Staff of the Army approved RECAP program critical to increasing the 11.5 ton load, 8 wheel drive HEMTT fleet armor ready capability. HEMTT-ESP remanufactures and upgrades 20+ year old HEMTT A0 and battle damaged A2 vehicles to the current A4 model.

The A4 HEMTT Variants offer improved survivability with an integrated underbody A-cab and a scalable B-kit (common to the Palletized Load System (PLS A1); an improved powertrain, suspension and electrical system and adds an anti-lock braking system, air conditioning and traction control.