The book is devoted to Soviet KV tanks, their creation and combat use during the Second World War. The first armored formation of the Red Army to receive KB tanks was the 20th Red Banner Tank Brigade. In this compound, prototypes of new vehicles were tested in battle during the assault on the Mannerheim Line. By July 1940, the brigade already had 10 tanks of the installation batch, armed with both 76-mm guns and 152-mm howitzers, which made it possible to begin training crews. This task was facilitated by the presence in the brigade of tankers who already had experience in military operations on new vehicles, and the deployment of the brigade in the Leningrad Military District. Nearby was Leningrad and the Kirov Plant, whose specialists provided tankers with assistance in solving operational problems that arose. However, the established rhythm of combat training was soon disrupted by the large-scale formation of tank troops.