The SMK tank (from the constructor Sergej Mironovich Kirov) was the only one from the "Leningrad Monster" series that came in to combat. The model was a variation (and possibly development) of T 35 from 1933 with same type of hull but in a more armour protected fashion. Though it had a good fire power its mobility was that of a snail and thus easy to hit for the anti-tank gunners. Stalin himself had expressed his opinion in the mid 1930s that heavy tanks was something to go for. The swamps at the Finnish front did agree and swollowed lots of them during the war.