G-792 M125 6x6 Prime Mover
- Weight: 31,600 lbs
- Engine: Le Roi T-H844 8-cylinder
- Displacement: 844 cu. in.
- Horsepower: 297 @ 2,600 rpm
- Fuel: Gasoline
- Fuel Capacity: 166 gallons
- Maximum speed: 42 mph
- Maximum range: 300 miles
When military strategists laid out the proposed post-WWII tactical vehicle families, the largest were the 10-ton G-792 series. Although several types were planned, only the tractor and the prime mover entered series production.
Initially, the Le Roi TH-844 V-8 gasoline engine powered both the tractor and the cargo truck. Mack began production of M123 tractors began in 1955 and ended it in 1957. In 1965, Consolidated Diesel Electric Company began production of a diesel version, designated the M123A1C. Most of the earlier trucks were converted to diesel, as well.
Originally, the M123 was intended to pull the M15A2 trailers. Later, the tractors were coupled with M162 60-ton lowboy trailers haul M60 main battle tanks.