The M939 is a 5-ton 6×6 U.S. military heavy truck. The basic cargo versions were designed to transport a 10,000 pounds (4,500 kg) cargo load over all terrain in all weather. Designed in the late 1970s to replace the M39 and M809 series of trucks, it has been in service ever since. The M939 evolved into its own family of cargo trucks, dump trucks, semi-tractors, vans, wreckers, and bare chassis/cabs for specialty bodies. 44,590 in all were produced.