by David Doyle
A ‘box design’ for safe troop transport
By the end of WWII, the U.S. military was looking for a fully enclosed, tracked, armored personnel carrier to replace the half-tracks then in service. The first, the M44 (T16) that was based on the M18 Hellcat, but it was huge, weighing 51,000 pounds and designed to carry 24 infantry soldier in addition to the driver, gunner, and commander. Ultimately, its size was its downfall – the army rejected the M44, noting that tactical doctrine called for 10-man infantry squads.
A set of requirements for a squad sized armored personnel carrier, based on the chassis of the T43 cargo carrier were issued on September 21, 1945. A little more than a year later, on September 26, 1946, the Army approved development of the T18 armored utility vehicle, giving a contract for four protoypes to International Harvester (IHC).
As originally proposed, the new vehicle would carry 14 soldiers (including the crew). IHC’s first prototype, the T18, dropped the assistant driver, Whereas the first prototype was armed with two remotely controlled machine gun turrets, the next pilot model, T18E1, pilot unarmed and had a high cupola for the commander. The T18E2 replaced the commander’s cupola with a T122 machine gun mount.
All of the prototypes were powered by the six-cylinder Continental AO-895-2 air-cooled gasoline engine exhausted through the hull side grills. Later, the T18E1 (the final configuration) was equipped with the AO-895-4 engine with the exhaust traveling through a pipe mounted horizontally across the front of the vehicle.
In 1952, the Army ordered 1,000 of the vehicles (now designated the “M75”) from IHC and an additional 730 from the Food Machinery and Chemical (FMC) Corporation. The production can be separated into two large group, “early” and “late” production. Early production vehicles made by International bear the serial numbers 7 through 376, while early FMC vehicles are numbered 1007 through 1326 (numbers lower than these were assigned to test units). Late production IHC vehicles run from 377 through 1006, while late production FMC M75s are numbered from 1,327 through 1,736.
The M75 established an interior layout that was copied in subsequent the two personnel carriers that would follow it: the M59 in 1954 and six years later, the M113 in 1960. The driver sat in the front left of the hull with the engine to his right. Immediately behind and in the center of the vehicle, sat the commander and infantry squad in a large compartment.
In later production vehicles, the driver’s position was equipped with an M19 infra-red night vision periscope in addition to the four M17 periscopes. The commander’s cupola could be armed with a machine gun, normally, a .50-caliber M2. When fully loaded, the crew compartment carried 1,800 rounds for the M2 in additions to an M20 “Super Bazooka” with 10 rockets, and 180 rounds of carbine ammo.
While the M75 proved itself in combat as reliable and powerful enough to meet the rigors of a fast-moving armored force, two factor ultimately led to its demise: Cost and size. Even though the steel-hulled M75 shared the same running gear as the M41 Walker Bulldog Light Tank, the $72,000 price tag on each APC made it too expensive to produce in the numbers the Army projected. Furthermore, the 41,500-lb. combat weight proved too heavy for amphibious operations. Having taken delivery of 1,729 vehicles, the Army halted any further production in February 1954.
A few of the M75s did make it into combat in Korea before the end of the war. Most were kept for training or auxiliary duties, while military aid provided 600 to Belgium, the only foreign military to use the M75 where they remained in service into the 1980s.