The T29 and T32 represented a divergence in the American heavy tank design after the development of T26 series heavy tank. The T29 with its large turret mounting the 105 mm gun, and the T32 with its ludicrously armored frontal protection are some of the main key distinctions between them. While the U.S. Armored Division would culminate their final heavy tank for service with the T26E3 Pershing for the rest of World War II, their development on even heavier versions did not end there.
Committed to developing the US heavy tanks even further, four new heavy tank projects were laid out as a response from the Army Ground Forces to modify the Pershing tank with heavier firepower and/or heavier protection. Two of those only required modifications on the T26 hull with no need to build an entirely new design. One was armed with a high velocity derivative of the Pershing’s 90 mm gun, known as the T26E4, and the other was reinforced with thicker armor casting at the front for increased protection, known as the T26E5. The remaining two had higher design requirements to fulfill that simply altering the main hull of Pershing simply wouldn’t be possible. Enter the T29 and T32 heavy tank.
The T29 sported a new high velocity 105 mm gun, something unheard of in the US tank armor development before. Such a large caliber cannon was not without a purpose, as it allowed the T29 to perform multi-purpose mission of destroying heavily armored fortification, while also engaging contemporary heavy tanks of the time on an equal footing, befitting for its role as a true heavy tank. However, the original T26E1 turret was simply not capable of mounting this rather cumbersome gun, and as such, a new turret design was urgently needed, a gigantic one.
A new power pack was provided to give enough propulsion for the T29, as its design and configuration bloated the tank’s combat weight by up to 22 tonnes from the Pershing, and only 4 tonnes lighter than the Tiger II, which proved to be a major liability in terms of logistics and transportation. However, its 105 mm was greatly appreciated for what it brought to the table, and was almost approved for mass production with a contract of 1200 units to participate in a cancelled plan for a full-scale invasion of Mainland Japan. It then continued endurance and engineering trials at home and was tested with various high caliber guns, resulting in two more variants to be developed, known as the T30 (155 mm), and the T34 (120 mm).
The T32, on the other hand, put more emphasis on being an impregnable mobile fortress from the front. The frontal armor consisted of a cast hull with 127 mm armor set at 54° and a cast turret with 298 mm of armor on the mantlet, which would give sufficient effective armor to deflect the most powerful AP shots of the time. The T32 would take a role as an assault tank, in the same lineage as the M4A3E2 Jumbo assault tank: Break through enemy defenses and exploit its heavily armored front to withstand enemy gunfires.
While this tank’s armor was loosely similar in term of armor construction as the T26E5, experiences from the M4A3E2’s combat in Ardennes demanded a more powerful engine to allow the assault tank to keep up with the spearheading forces. Therefore, an upgraded power pack consisting of a V12 engine and a cross-drive transmission was produced. That would mean a new, lengthened hull was preferred instead of retaining the original Pershing hull, which would leave not much room to install the new engine and transmission. Though, unlike the T29, the T32 had a more tolerable combat weight at 54 tonnes, just short of 3 tonnes than the Tiger I. However, the T32 was only partially finished by the end of the war, and only produced in limited number, generating one last variant with all-rolled front hull armor instead of cast, designated as the T32E1.
The T32 unfortunately was met with a development dead end, as the Pershing-based hull was quickly getting phased out by the Army, in favor of a relatively novel tank design in the 50’s. The 90 mm high velocity cannon was considered inadequate in combating the prevalent Soviet armor as well. Instead, the large caliber gun development from the T29 series finally found its usefulness when the T34, with its 120 mm T53 cannon, was improved even further, paving way into the development and production of the M103 Gun Tank.