World War Photos

M33 Prime Mover towing a 240 mm gun. Italy 1944

The M3 Lee medium tank served as the basis for several projects aimed at developing a tracked prime mover for heavy artillery during World War II. These attempts reflected the U.S. Army’s need for reliable, armored vehicles capable of towing large-caliber artillery pieces, as the demands of the battlefield evolved.

T2 Heavy Tractor

• Origin: The T2 was an early attempt to create a heavy tracked tractor, using components from the M2A1 medium tank.
• Trials: Conducted in 1941-42, these trials were deemed unsatisfactory, primarily due to performance and reliability issues. This led to the abandonment of the T2 concept.

T16 Heavy Tractor

• Design: Developed as a follow-up to the T2, the T16 used the M3A5 medium tank chassis, part of the M3 Lee/Grant series.
• Performance: Mechanically, the T16 was considered satisfactory, with decent automotive performance. However, it faced a significant issue with inadequate internal stowage, which limited its practicality for towing heavy artillery and transporting equipment.
• End of Project: By 1943, the T16 project was discontinued in favor of focusing on unarmored tractors, which proved to be more efficient and cost-effective for artillery towing duties.

T23 and M6 High-Speed Tractors

• Development: The T23 tractor was introduced as a solution to the U.S. Army’s need for a heavy artillery prime mover. It was an unarmored vehicle and proved to be more suitable for the role.
• M6 High-Speed Tractor: The T23 eventually received the official designation as the M6 high-speed tractor, but its development suffered from delays and a prolonged gestation period, affecting its availability for immediate use during the war.

M33 Prime Mover

• Need for an Immediate Solution: With the T23/M6’s delays, the U.S. Army had an immediate need for a heavy artillery tractor in the field. As a result, the Chester Depot was tasked with converting 109 M31 tank recovery vehicles (TRVs) into the M33 prime mover from December 1943 to March 1944.
• Conversion Process: The conversion involved removing the turret and crane assembly of the M31, but retaining the internal winch, which was a crucial component for towing heavy loads.
• Usage: The M33 was primarily used to tow super-heavy artillery, such as the 8-inch gun M1 and the 240mm howitzer, both of which were crucial for long-range bombardment and siege operations.