The KV-8 heavy flamethrower tank. The reconstruction of the turret of the tank above

During this time, versions of the T-26 light tank (OT-26, OT-130 and OT-133) were used as flamethrower tanks. However they were too weak and too light. The experience of the Winter War showed that flame tanks became the first targets for any anti-tank defense. That's why more powerful and better protected tanks were needed. So, Soviet tank designers decided to re-equip T-34-76 and KV-1 tanks with flamethrowers.

The new ATO-41 flamethrower was mounted in the hull of the T-34 (in place of the bow TMG) and in the turret of the KV-1 (in place of the coaxial TMG). Unfortunately, the KV's turret hadn't enough room to mount both the ATO-41 and the 76.2 mm gun, so this gun was replaced with a 45 mm gun mod. 1932. The thin barrel of this gun was camouflaged with a special gun jacket to simulate the common 76.2 mm gun.

The KV-8 had 92 rounds for the 45 mm gun and 107 shots for flamethrower with a total of 960 litres of gas mixture. In addition the tank had a bow DT TMG and a DT in the rear of the turret. Also, some tanks were equipped with a DT AAMG. Total ammunition for the machine-guns was 3400 rounds.

The ATO-41 could fire up to three times in every 10 seconds. Each shot took about 10 litres of gas mixture. The range of the flamethrower depended on the type of gas mixture:
- 65 litres with 60% mazut and 40% kerosene;
- 100 litres with kerosene-oil mixture.

The production of the KV-8 tank began in 1942. The main advantage of the KV-8 over the OT-34 was the capacity of gas mixture. The KV-8 and the OT-34 were organized in separate battalions of flamethrower tanks (The Chemical Tank Battalions).

The KV-8S heavy flamethrower tank.

Each battalion have had two KV-8 tank companies (10 tanks per battalion) and one OT-34 tank company (10 tanks plus one commander's OT-34). After production of the KV-1 was canceled, the KV-8 tank was based on the KV-1S. It was renamed as the KV-8S. The ammunition of the KV-8S was increased up to 114 rounds (for the 45 mm gun), 60 shots for the flamethrower and the gas mixture capacity was decreased to 600 litres. During production, the ATO-41 flamethrower was replaced with the more modern ATO-42. The weight of the KV-8S was 43 tons. It had a crew of 5 men.