Combat experience of the experimental KV heavy tank in Karelia in December of 1939 showed that its armour held up very well against Finnish AT guns. However, the 76 mm gun was not powerful enough to combat concrete bunkers. The Military Committee of the North-Western Front sent a request to the Kirov factory: manufacture 4 KV tanks with a heavy gun, capable of destroying bunkers and anti-tank fortifications.
The project had to be developed quickly, since the Red Army was stuck on Finnish defenses. Engineers worked 18 hours a day, and finished the project in merely two weeks.
The new KV was armed with a 152 mm M-10 howitzer model 1938/40. It would never fit into the standard KV turret, and SKB-2's engineers created a large, rectangular turret for it. This turret, almost twice as large as the existing one, fit on the same turret ring.
The KVs were divided into two types. KVs armed with a 76 mm gun were officially named "tank with small turret". 152 mm howitzer armed KVs were called "tank with large turret". The KV-1 and KV-2 indexes we are used to were only assigned in 1941.
In February of 1940, these new tanks arrived in Karelia. They were put into a special heavy tank company under the command of captain Kolotushkin. Aside from the KVs, the company contained an experimental two-turreted T-100 tank. Unfortuntately, the KVs never got to test their might against Finnish fortifications. By the time they arrived, the Finnish defenses were overrun. Regardless, according to the KV crews, the new "heavyweights" destroyed 14 AT guns and 11 bunkers.
When shooting at granite-concrete anti-tank fortifications, it was found that if the fortification was not dug into the ground, it was simply flung to the side, or broken into pieces. This was still not enough to make a path, and sappers had to be called in.
Combat in December proved the KV's resistance to AT shells once again. Finns would often simply stop firing after several nonpenetrating hits. However, mines were a problem. As is proper for a breakthrough tank, the KV went first, and hit the minefield first. Damaged tracks and front wheels were common.
The Winter War showed many weaknesses of the KV-2 design. Their large mass caused them to sink in mud. The massive gun demanded that the KV-2 fired while stationary, hopefully on flat ground. Firing the 152mm howitzer during movement or while tilted could damage the tank. Furthermore, the small turret ring meant that shooting perpendicular to the hull was a bad idea. The turret might get jammed, or, even worse, the massive recoil would cause damage to the engine or transmission.
During the KV-2's lifetime, the production of sufficiently reliable parts. The gear box, in most cases, could not last the warranty period. Poor filters led to tanks breaking down after traveling on dusty roads. The cooling system worked poorly. The steering clutches broke constantly. No demands of the manufacturers could improve the situation.
The tank had poor visibility, and its large mass proved to be a problem not for it, but also for others. Not only was the KV limited in what terrain and bridges it could cross, but after passing through a road, it was often made unusable by wheeled vehicles.
By June 1941, 132 KV-2s were present in the Red Army. Only 20 of them could fight right away; the rest were either undergoing repairs or had no crews. A lack of experienced crews was a problem in general. The KV was a very different tank from a T-26 or a tankette, which many tank crewmen were trained on.
All of the drawbacks listed showed up at the start of the Great Patriotic War. They were further compounded by the lack of competent leadership. Commanders lacking battle experience often issued incorrect or contradicting orders. Tanks were often redirected, sometimes more than once per battle, which led to many pointless marches. KV tanks frequently broke down during these marches. If the tank broke down and there were no engineers nearby, it had to be abandoned, and, preferably, blown up. Even if there were engineers, the tank had to be towed. Damaged tanks were towed by Voroshilovets tractors. In the case of the KV, two tractors had to be used. One was simply not up to the task. During the first days of the war, the rapid advance of the German forces made evacuating tanks very difficult, and many were captured.
However, the KV-2 was not all bad. In the cases where KV-2s engaged the enemy, they could hold their own. Soviet heavy tanks were impervious to most of the Wehrmacht's AT guns, and one hit from the 152 mm howitzer was the end for any German tank. Numerous KV tanks, under enemy fire, calmly crossed into their positions, and simply ran over the AT guns. The same fate was in store for German tanks, especially light ones. KV tanks with experienced crews and competent commanders could deliver significant damage to the enemy. Sadly, in the first days of the war, there were very few of those.
KV-2 tanks stopped being produced in October of 1941. The reasons given were the technical problems with the vehicle, and the fact that the army had no need for a KV-2 at the start of the war. The 76 mm gun on the T-34 and KV-1 could do the job sufficiently well. Add to this the amount of materials that the KV-2 took, and this colossus was doomed to extinction.
The last KV-2 was used in combat during the Battle of Moscow in the 1941-42 winter. A turret from one tank outlasted the tank itself. It was mounted on the armoured train "For the Motherland", which fought in the southern direction until July 17, 1942, when it was destroyed by German bombers.
The only 100% authentic KV-2 is currently on display at the Central Museum of the Armed Forces in Moscow.
Original article available here.