The M8 75mm Howitzer Motor Carriage was a successful attempt to mount a howitzer in the chassis of an M5 light tank, and was used in combat from late in 1943 until the end of the Second World War.
Early in 1942 the Armored Force examined two alternative methods of mounting a 75mm Howitzer on the chassis of the M5 Stuart light tank. The T41 HMC had the gun mounted on a standard mount in an open topped fighting compartment. A mock-up was produced, using the correct chassis and gun but with an un-armoured superstructure, but this was abandoned in favour of the T47.
The T47 went for an alternative method of carrying the 75mm gun. The normal M5 turret was removed and a new larger open topped turret was designed. This required a larger turret ring, which in turn meant that that fighting compartment was expanded slightly. The T47 used the twin Cadillac engines of the M5 Light Tank, and also kept the suspension, final drive and gears of that vehicle.
Earlier attempts to mount a howitzer on the chassis of a light tank had all used the same method as the T41 and had failed because of a lack of space for the crew and limited protection behind the gun shields or walls of the superstructure.
A mock-up of the T47 was ready by April 1942 and went for tests at the Aberdeen Proving Ground. The open turret was found to a far superior design to the fixed fighting compartment, allowing for a fully traversable gun with a great range of elevation. It also provided greater crew protection, although the open top was a vulnerability.
The T47 was accepted for production as the M8 75mm Howitzer Motor Carriage. Cadillac built a total of 1,788 M8s between September 1942 and January 1944.
The M8 began to enter combat late in 1943 and was used in the HQ companies of tank battalions to provide fire support. The M8 was used during the Italian campaign, remaining in use into 1945. In April 1945 it was being used by the HQ Company of the 758th Tank Battalion, a segregated battalion manned by African-American troops.
The M8 was also used in Normandy and the campaign in north-western Europe. It fought in the bocage county where the open top of the turret made the crew vulnerable to small arms fire. It remained in use to the end of the war in Europe. Some took part in the fighting at Bastogne during the battle of the Bulge.
The M8 was also used in the Pacific. If was used on Saipan in June 1944, providing fire support for light tank companies. Each armoured cavalry squadron also had six M8s. They were used on Biak in July 1944 and on Leyte. In September 1944 the 81st Infantry Battalion had six M8s at the start of the invasion of Angaur in August 1944 and used the surviving vehicles on Peleliu in September-November 1944.
Some were converted to act as command vehicles. Brigadier General George Read, assistant divisional commander of the 6th Armoured Division used an M8 with the turret removed and a fixed armoured superstructure as his personal commander vehicle.
After the end of the war the M8 was quickly phased out of American service, and many were given to American allies. The French used them in Indo-China and they were part of the equipment of the South Vietnamese army. They were used in Vietnam until the early 1960s.