The T19 105mm Howitzer Motor Carriage was an expedient design that mounted a standard 105mm howitzer on the chassis of an M3 half-track.
In the autumn of 1941 the US Army Ordnance Department ordered work to begin on mounting the 75mm and 105mm howitzers on half-tracks as a short-term expedient while more suitable fully tracked vehicles were under development. The T30 75mm Howitzer Gun Carriage was a fairly simple project, but there was some concern that the M2A1 105mm howitzer was too heavy and too powerful for the M3 chassis. As a result two projects were begun. The T38 105mm Howitzer Motor Carriage was designed to take a lighter T7 105mm pack howitzer, while the T19 105mm Howitzer Moto Carriage used the M2A1.
The T19, T30 and T38 shared a common basic layout. The howitzer was mounted on a table at the front of the fighting compartment, allowing it to fire horizontally forward. The fuel tanks were moved to the back corners of the compartment, and a machine gun mount was located at the rear. Storage arrangements differed between the designs.
The T19 was ready for tests early in 1943 and it was authorized for service use on 25 March 1942. At the same time the T38 was cancelled. A total of 324 T19s were produced by the Diamond T Motor Company, but production then ended in favour of the much superior M7 105mm Howitzer Motor Cannon 'Priest'.
The T19 was issued to the cannon companies of infantry divisions in North Africa, each of which got six T30 75mm HMCs and two T19 105MM HMCs. They were also used by the artillery battalions of the armoured divisions, although the 1st Armoured Division was the only one to use the T19 in combat.
The T19 made its combat debut during Operation Torch, the Allied invasion of North Africa in November 1942. A small number of T19s and T30s were landed at Oran and Algiers to support the infantry that made up the bulk of the landing force. The T19 was used during the campaign in Tunisia, including the battle at Kasserine Pass.
The T19 was used in Operation Husky, the invasion of Sicily of July 1943, but by that point it was already being replaced by the M7 105mm Howitzer Motor Carriage 'Priest' in most units. The Cannon Company of the 16th Infantry was awarded a Presidential Unit Citation for its actions near Gela, on Sicily, in June 1943, where it used its T19s to help repulse an attack by the Hermann Goring Panzer Division, destroying a number of tanks.
A small number of T19s remained in use in Italy although the numbers available slowly declined. They were also used during Operation Dragoon, the invasion of the south of France of August 1944.