The origin of the IS-1 project came from numerous reports regarding the KV-1. Even in its faster version, the KV-1S, offered no greater fighting capabilities than the T-34, while costing much more and being more labor intensive. Stalin nearly cancelled all heavy tank development in 1943 but, in that summer, the Panther and Tiger were seen in action. Heavy tanks had to be improved, both in protection and firepower, to adequately cope with the new threats.
In March 1943, an order specified the rearming of all frontline tanks. One of the guns intended for this was an AA gun roughly similar in performance to the German 88 mm (3.46 in), of which one had been disabled, captured and the gun analysed. This resulted in the stopgap KV-85 heavy tank, only produced in limited numbers (143 machines). This vehicle set the tone for further improvements, being the basis of the long “Iosif Stalin” series. The KV-85 turret was brand new, well adapted to the new gun designs. It could hold three men, but the hull remained basically the same KV-1 flat-armored hull first designed for the multi-turreted SMK back in 1939.
The IS-85 (Obyekt 235) prototype started its successful but rushed trials in mid-1943. Production was assumed by Chelyabinsk Kirov Plant. The first IS-1 (definitive series vehicles) rolled of the line in October 1943, but it was stopped in January 1944, as the IS-1 was quickly replaced by the all-better IS-2. Because of this, only 200 to 207 were produced. However, it was a considerable improvement over the previous KV-85 and the T-34/76. The appearance of the new T-34/85 medium tank caused the IS series to evolve, and to be logically up-gunned. So, in January 1944, many IS-1s not yet delivered to the front were up-gunned. The IS-1 also tested a new 100 mm (3.94 in) gun and went into comparative trials with the IS-122, favorable to the latter. The new A-19 122 mm (4.80 in) gun had the punch to get through the armor of a Tiger at medium range.


Dimensions:

Hull length: 6.6m - 8.56m with gun
Width: 3.07m
Height: 2.74m



Ingame:

Hull length: 10 blocks - 13 blocks with gun
Width: 5 blocks
Height: 4 blocks
Scale: 1.5:1