History
Early battle reports in World War II emphasized the urgent need for highly mobile artillery to keep pace with fast-moving tanks during advances. At the time, the US Army lacked such a critical asset in its armored divisions. To resolve this, in October 1941, Major General Jacob L. Devers requested the development of a 105 mm howitzer motor carriage based on the M3 Medium Tank chassis as part of the broader rearmament and modernization efforts in preparation for the impending conflict.
Two prototypes, designated T32, were constructed using the standard M3 Lee medium tank chassis, replacing the armored compartment and turret with a large, open-topped superstructure. These underwent extensive testing to identify and resolve various issues before further modifications were implemented. By April 1942, the M7 Howitzer Motor Carriage (HMC) was standardized and approved for mass production.
The M7 was armed with a 105 mm M2A1 howitzer mounted slightly to the right of the vehicle’s centerline. While the prototypes carried 57 rounds, the production M7 increased this capacity to 69 rounds by removing crew seats to make room for extra rounds. The howitzer fired standard ammunition types, including high explosive, anti-tank, white phosphorus, and smoke shells, with a maximum range of approximately 6.5 miles (10.4 km). It could sustain a firing rate of eight rounds per minute, equating to a reload time of about 7.5 seconds. A .50 caliber M2 anti-aircraft machine gun was mounted on the upper starboard corner, leading to the vehicle’s nickname, Priest, as the gun mount resembled a church pulpit. The machine gun was positioned on a small ledge attached to the mount and hull, with later models extending the pulpit further down the hull. The M7 was typically operated by a crew of seven.
Like the prototypes, early-production M7s retained the three-piece differential and final drive housing from the M3 Medium Tank, identifiable by the rectangular cutout on the upper right section. They also used the riveted lower hull and early vertical volute spring suspension from the M3. Later production models transitioned to components from the M4 Sherman, including the single-piece casting without the cutout, a welded lower hull, and heavy-duty suspension bogies.
The M7 was powered by a Continental R975 air-cooled radial engine, also used in Sherman tanks, enabling a top speed of 24 mph (38.6 km/h). Early models featured the same vertical volute suspension system as the M3, with a centrally mounted track return roller above the bogie assembly. A heavier-duty bogie assembly, with the return roller mounted at the rear, was introduced in mid-1942. However, due to supply priorities favoring the heavier M4 Sherman, only later M7 models received this upgraded suspension once resources became more readily available.
The M7 Priest first saw combat during the summer of 1942 at El Alamein with British forces in North Africa, supplied through the Lend-Lease program. Later that November, American forces deployed the M7 during Operation Torch. Throughout World War II, the M7 Priest provided continuous artillery support to Allied armored units in Northwest Europe and the Pacific, with three battalions typically attached to each US division.
The M7 proved reliable enough to remain in service long after World War II, including during the Korean War. A total of 3,490 M7 Priests were manufactured before production ended in the spring of 1945. Two improved variants were later introduced: the M7B1, based on the M4A3 chassis, and the M7B2, with increased elevation for Korean War conditions. After the Korean War, remaining M7s were either scrapped or distributed to US allies under military aid agreements.
