The Soviets were one of the few nations still experimenting with the “land battleship” concept in the late 1930s, with impractical beasts such as the T-100 and SMK. As soon as development seemed like it took a more rational direction with the KV-1 and its heavier counterparts, the T-150 and T-220, rumors of a German 90-tonne tank catalyzed the development of even larger tanks, with the heaviest being the KV-5, weighing 100 tonnes. Work only reached the blueprint stage when its designers were evacuated to Chelyabinsk due to the German forces approaching Leningrad.