Flamethrower tanks were intended for assaulting heavy entrenchments because of their great psychological effect. In November 1941, in Chelyabinsk, work on the KV-8 tank began. Under the Soviet pre-war tank theories, all flamethrower tanks were counted as a part of the Soviet Tank Army.
During that time, some 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 and KV-1 tanks with flamethrowers.
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.
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.
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 ("Chemical Tank Battalions" - according to Soviet designations).
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 KV-1S. It was renamed as KV-8S. The ammunition of the KV-8S was increased up to 114 rounds (for the 45 mm Main 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.
Sources: "M-Hobby" #5-6 1997 V.Gagin "Heavy breakthrough tank Klim Virishilov" Poligraph 1996 "Soviet heavy tanks in WWII", Tornado