The Uralvagonzavod IS-51 is a superheavy breakthrough tank used by the Mecharussian Armed Forces. Entering service in 2151 under the initiative of Grand Marshal Gordon Kravchenko, it carries on a long-standing MAF tradition of naming superheavy tanks after Soviet leader Joseph Stalin.
Because Kravchenko was killed in action in the Main Canon and the sole prototype destroyed before the vehicle could even be commissioned for production, the IS-51 is only present in the Alternative Canon. In the Main Canon, its equivalent is the ET-60, which enters service nine years after the IS-51 was supposed to have been.
The IS-51 replaces the older IS-44 model, over which it possesses a number of advantages - it is much lighter, able to be carried in a cargo sling by a Tu-245 heavy dropship, faster and is equipped with a rotating turret as opposed to the IS-44's casemate design. While it retains the phenomenally-heavy armour of its predecessor thanks to advancements in nanometallurgy, the gun has been downsized on the production model by almost a third, from 300-millimetres to 203-millimetres, as a weight-saving initiative. However, the weapon system is actually even more powerful, being chambered to fire pure-fusion nuclear warheads as opposed to the antimatter high-explosive shells of the 300-millimetre howitzer.