The joint American-British T14 Heavy Tank assault tank program began in the early part of World War 2 (1939-1945) when both nations sought upgrades to their existing M4 Sherman and Churchill Infantry Tank lines to compete with the latest in German tank offerings. While both proved effective designs, the Sherman lacked armor protection and the Churchill proved a plodding armored beast. The T14 would solve both issues in one jointly-developed form to which the owners would then fit local armament and equipment to and operate them as needed. The optimistic program netted just a pair of pilot vehicles during which the Shermans and Churchills evolved into improved forms which negated the need for a new, all-purpose machine. The T14 program was then cancelled in short order, the two prototypes evaluated and ultimately discarded by the two nations. Some of the work influenced the ultimately abandoned T20 Medium Tank program for the Americans - what would have become the successor to the M4 Sherman line.
The charge to construct the two pilot vehicles fell to the American Locomotive Company. Orders were already secured in 1942 but progress on the models proved slow in the face-paced environment of war. The prototypes were not readied for formal evaluations until 1944 to which by this time the other tank lines had grown into successful (or adequate) combat platforms when combined with air strikes via air superiority, advancements in portable anti-tank weapons at the infantry level, and the rise of dedicated tank destroyers and assault guns. The T14 program was, therefore, not advanced beyond these two prototype vehicles. While providing the needed armor protection sought, the design was just as slow as the Churchill and offered little benefit beyond that.
As completed, the T14 became a 41-ton, heavy-class vehicle fitting either the British 57mm QF 6-pounder or American 75mm M3 main gun Local defense was through 2 x 0.30 caliber machine guns as well as an optional 0.50 caliber heavy machine gun for air defense. Power was served through a Ford GAN V8 engine of 520 horsepower, giving the vehicle a maximum speed of 17 miles per hour with a range of 100 miles. Armor protection was 133mm at its thickest. The design incorporated a rear-mounted engine, sloped armor and a turret fitted at center. The track-over-wheel arrangement saw six double-tired road wheels arranged across three individual support units with the drive sprocket at front and track idler at rear. Side armor contoured well over the upper track sections from the sloped superstructure hull sides. 50 x 75mm projectiles were to be carried for the main gun and up to 9,000 rounds of ammunition for the 0.30 caliber weapons. The crew complement numbered five and was made up of a driver, assistant driver, gunner, loader, and commander. Dimensions included a running length of 20 feet, 4 inches, a width of 10 feet, 5 inches and a height of 9 feet, 10 inches.