Dukhov's team was instructed to create a stopgap KV tank, the KV-85, which was armed with the 52-K-derivative gun of the SU-85, the 85 mm D-5T, that proved capable of penetrating the Tiger I from 1,000 m (1,100 yd).

The D-10 had been designed for anti-tank fire and had better armor penetration than the A-19, but the smaller caliber meant it had a less useful high explosive round.

The D-25 used a separate shell and powder charge, resulting in a lower rate of fire compared to the single-piece ammunition used in most tanks, a serious disadvantage in tank-to-tank engagements.

[15] According to the same Wa Pruef 1 report, it was estimated that at 30 degree obliquity the hull armor of the Soviet IS-2 model 1943 would be defeated by a Tiger I between 100 and 300 m (0.062 and 0.186 mi) at the driver's front plate and nose,[16] while the IS-2's 122 mm gun would penetrate the Tiger's front armor from between 500 and 1,500 m (0.31 and 0.93 mi).

[17] However, in the summer of 1944, the Germans experienced a shortage of manganese and had to switch to using high-carbon steel alloyed with nickel, which made armor very brittle, especially at the seam welds.

[23][24] The IS-2's armour was primarily composed from casting, which involves pouring molten metal into a mold and letting it cool.

This method was done to reduce production costs and thus increase the number of vehicles that could be built (in contrast to its contemporary the Tiger II, which required significant machining in its construction).

Casting also made it easier to vary the shape and thickness of the armour, which also reduced the exterior surface relative to tank volume.

Lower-quality alloys had to sometimes be used, substituting manganese for nickel, meaning that while the armour had high hardness and resisted penetration better than steel, it was also quite brittle and thus at risk of shattering.

It was slightly lighter and faster than the heaviest KV model 1942 tank, with thicker front armor and a much-improved turret design.

Western observers tended to criticize Soviet tanks for their lack of finish and crude construction.

The Soviets argued that it was warranted, considering the need for wartime expediency and the typically short battlefield life of their tanks.

In late 1944, the stepped hull front was replaced with an improved single casting of 120 mm thickness angled at 60 degrees.

Other minor upgrades included the addition of a travel lock on the hull rear, wider mantlet and, on very late models, an anti-aircraft machine gun.

[28] The special tank regiments were reserved for important attacks, often to spearhead attempts to break through fortified German positions like anti-tank defence lines and bunkers.

[28] The tanks supported infantry in the assault by destroying bunkers, buildings, dug-in weapons and engaging German armoured vehicles.

Later in the day, Soviet forces counter-attacked and seized the town of Oględów and found three abandoned Tiger IIs.

In the late 1960s the remaining Soviet heavy tanks were transferred to Red Army reserve service and storage.