Due to the emergence of the German Tiger I heavy tank, the US Army designed the M26 Pershing medium tank. It was redesignated as a heavy tank strictly for morale, but did not rectify the problem that worsened in 1944. Heavier and stronger German AFVs were appearing in 1944 and the M26 Pershing was not equipped to deal with these greater threats. In OCM 25117 on 14 September 1944 recommended for development and manufacture of four pilots for a new heavy tank. Two were designated as T29 heavy tank armed with a T5E1 105mm Gun while the other two were the T7 155mm Gun armed T30 heavy tank. OCM 26825 of 1 March 1945 suggested procuring 1,200 T29 heavy tanks. It would be powered by the new Ford GAC, V-12, liquid-cooled engine (770hp at 2800rpm) paired with the new General Motors CD-850-1 cross drive transmission (a single unit combining transmission, brakes, and steering gear).
The hull-mounted MG was a M1919A4 .30in cal. The T5E1 105mm Gun had two coaxial M2 .50in cal HMGs in the gun mantlet with a pedestal mount on the turret roof for an additional M2 .50in HMG for anti-aircraft use. The T5E1 105mm Gun when firing the T32 AP achieved a muzzle velocity of 3000ft/s, the T29E3 HVAP a maximum of 3700ft/s, and the T30E1 HE only 2500ft/s.
Procurement of the T29 heavy tank was approved 12 April 1945, but order reduced to 1152 units. In that same month four additional T29 pilots were approved, but one would be armed with the T53 120mm Gun and designated as the T34 heavy tank. Pressed Steel Car Company, Inc. managed to finish one T29 and partially finish another by the end of WW2. All material was transferred to the Detroit Arsenal with ten more pilots completed for post-war development programs that would provide invaluable information for the entirety of the Cold War.