The KV heavy tank replaced the five-turret T-35, a land battleship whose thin armor the Spanish Civil War showed could not survive modern anti-tank guns. Designer Joseph Kotin turned away from the twin-turret SMK concept, built a single-turret design and put the saved weight into thick frontal armor, naming the result for defense commissar Kliment Voroshilov. Tested in the 1939 Winter War against Finland, it outperformed its competitors, and the KV-2 variant carried a 152mm howitzer to destroy concrete bunkers at close range. When Germany invaded in June 1941, German intelligence had missed the tank entirely, and 37mm and 50mm anti-tank rounds bounced off its sloped armor; German infantry called it the Russischer Koloss.

At Raseiniai in June 1941 a single KV held up the 6th Panzer Division for a day, knocking out 50mm guns and an 88mm flak gun before a second 88 fired from behind. In August 1941 near Krasnogvardeysk, Lieutenant Zinoviy Kolobanov’s five dug-in KV-1s destroyed 43 German tanks in half an hour, and his own tank took 135 hits without a penetration. The 45-ton KV was too heavy for many bridges, had poor visibility and a gearbox based on a Holt tractor design that drivers reportedly beat into gear with hammers. Better German guns and the Hs 129 made it vulnerable by 1942; appliqué armor raised it to 52 tons, the lighter KV-1S traded armor for speed, the KV-85 arrived in small numbers, and Voroshilov’s fall cleared the way for the IS series.

• At Raseiniai, German engineers placed satchel charges on the KV overnight, and infantry finally had to drop grenades through holes punched by an 88.
• Kolobanov hit the lead and trailing German tanks first, trapping the column on a swampy road where narrow tracks bogged down.
• Factories were being evacuated east to the Urals in 1941, so the Soviets kept building the flawed KV rather than pause production.
• The KV-1S got a planetary transmission and could exceed 43 kilometers per hour.
• The KV-8 hid a flamethrower in its turret behind a fake wide tube around a small 45mm gun, while the KV-1K bolted rocket launchers to the hull.