Beginning in 1945, several new tank designs were drawn up to replace the IS-2. Object 703 was not the first new design, but it was the first to enter production, hence its designation of IS-3. The title of IS-4, meanwhile, went to Object 701, which took longer to develop. This tank had an overall design much more similar to that of the IS-2, simply larger. The chassis was lengthened, having an additional pair of road wheels, and the angles on both the turret and hull front were more severe. However, the IS-4 offered no significant advantage over the IS-2 other than a faster rate of fire, and was a much more complicated machine to produce. Two experimental tanks were drawn up that used the exact same hull, but with different running gear to support a heavier turret: the ST-1, which had the further advantages of greater gun depression and magazine capacity at the cost of increased weight, and the ST-2, which was the same but with two guns. Neither left the drawing board before Zhosef Kotin started yet another project.