SU-100Y – The Soviet “Boxtank”

Su-100Y

While fighting the Winter War against Finland the Soviets started development on a bunker-busting self-propelled gun named the SU-100Y. It was created by placing a powerful 130 mm naval gun on the chassis of the T-100 heavy tank.

Though technically designed to eradicate fortifications, the SU-100Y would have made light work of any German tank unfortunate enough to find itself in its sights.

Its an extremely simple design, with flat sided armor, no machine guns and it doesn’t even have hatches for the crew.

By the time the SU-100Y was complete the Winter War had ended and the Soviets had little use for this 60 ton beast. However the single SU-100Y built was reportedly pulled out of storage and used to help defend Moscow in 1941.

Some say that this mighty machine saw even more action, remaining operational until the war’s end.

T-100 Heavy Tank

As mentioned, the SU-100Y was built on the chassis of the T-100.

The T-100 was a large tank designed by Factory N°185, in the Bolshevik Factory in Leningrad in the late 1930s as a potential successor to the rather lacklustre T-35. It directly competed against the SMK, a similar looking and equally large tank from the Kirov Plant, also in Leningrad.

The SMK was named after communist politician Sergei M. Kirov (SMK).

The T-100 heavy tank, the basis of the SU-100Y. The multi-turret design added significant weight, and overcomplicated the commander’s job.

Both the T-100 and SMK had two turrets – less than the five-turreted T-35 – but probably still a bit too much. The use of multiple turrets was something of a Soviet fascination at the time, partly because of its theoretical capabilities (more guns = better, right?) and propaganda effect.

In reality though a tank with multiple turrets will be much bigger and heavier, or have thinner armor to keep the weight down. The crew's job is made harder, and the commander has to maintain control over where the tank is going, and what the turrets are doing.

On both, the larger turret contained a 76.2 mm gun, and the smaller sub-turret contained a 45 mm gun.

The T-100 weighed 64 tons, had a crew of seven and was extremely long. Because of the tank’s massive size it had poor mobility and unimpressive armor.

It was around this time that the Soviets began listening to designers, who knew multi-turreted tanks weren’t very good. On their own initiative, the SMK’s design team created another heavy tank in parallel to the SMK that only had one turret. It was smaller than the SMK and carried more armor all while weighing 8 tons less. This single-turreted tank would become the KV-1.

The T-100’s competitor, the SMK. A modified version of this tank with a single turret became the KV-1.

The Soviets sent the SMK and T-100 prototypes over to Finland for a literal baptism of fire in combat, where their large size, cumbersome performance and overly complicated offensive armament limited their effectiveness.

Ironically neither the T-100 nor the SMK would enter production, with that achievement instead going to the KV-1.