The IS-4M is an improved modification of the fourth variant of the IS heavy tank family. Like the IS-3, the IS-4 (designation Object 701) was intended to replace the IS-2. The IS-4 was designed to be the pride of the Soviet Army, with extremely thick armour, a weight of 53 tonnes, and a 750 horsepower V-12 diesel engine capable of reaching speeds of up to 43 km/h. Despite being an upgrade to the IS-2, it never offered much to the table, particularly when compared to the IS-3, a lighter, faster, and cheaper tank that had stunned the Western world only a few years previously.