tank destroyer, was rapidly becoming obsolete, because its main armament, the 3-inch gun M7, had difficulty defeating the thick frontal armour of these new tanks past several hundred yards. In late summer 1942 American engineers had begun examining the potential of a new tank destroyer armed with a 90mm gun. This study resulted in a prototype vehicle, the 90 mm Gun Motor Carriage T53, which placed the 90 mm gun in an open mounting at the rear of an M4 Sherman chassis. In August 1942, it was agreed to immediately produce 500 vehicles, with 3,500 more later. The Tank Destroyer Force objected, arguing that the design of the T53 was too rushed. The 90 mm Gun Motor Carriage T53E1 proved to be even worse, and the entire contract was canceled. In October 1942, the Ordnance Department tested mounting the experimental 90 mm gun T7 into the turret of an M10 tank destroyer. General Andrew Bruce, head of the Tank Destroyer Force, objected to the project, favoring the lighter Gun Motor Carriage M18 'Hellcat', but was ignored. Mounting the 90 mm gun was straightforward, but the gun proved too heavy for the M10's turret. A new turret was designed that incorporated power traverse and a massive counterweight to balance the gun. The first two M36 prototypes, designated 90 mm Gun Motor Carriage T71 were completed in September 1943. Initially, a request for full production was denied as 90 mm guns were already being studied for use on tanks, but Army Ground Forces approved the project in October 1943, and tests began. The ring mount on the left side of the turret for the .50 caliber Browning M2HB antiaircraft machine gun was changed to a pintle mount at the rear. It was decided that production vehicles would use the chassis of the M10A1 tank destroyer, as significant numbers of M10A1s were available, and it was determined that the M10A1 had superior automotive characteristics. After testing, an initial order for 300 vehicles was issued. The T71 was designated upon standardization on 1 June 1944 as the 90 mm Gun Motor Carriage M36. Production After July 1943, the appliqué armor (add on armor) bosses on the hull side of the M10A1 were deleted as the armor kits were never manufactured. This meant that some M36s had the redundant bosses, while others did not. The M36 initially retained the M10A1's "stirrup" gun rest on the