The KV-1 was a Russian heavy tank designed in 1938-39. It was armed with a high velocity 76mm main gun, and was protected by 75mm of armor in earlier productions and up to 130mm in later productions. One of the downsides of the KV-1 was its low mobility. It had a top speed of 35 kph in normal conditions, and the later models had a top speed of only 28 kph. Furthermore, the steering was horrible, and the transmission was famous for having to be changed with a hammer. The tank had many variants, such as the KV-2 and the KV-3, but many of these never made it past the prototype phase. It came as a nasty surprise to the Germans when they first invaded as they had no heavy tanks to counter them. A Pz III or IV had to shoot a KV-1 point-blank in the back to penetrate it's thick armor. One of the variants (KV-5) will be introduced in a future update.
This is the Russian tier IV tank. Like in real life the KV-1 has good armor and can do a lot of damage, but it is slow. Do not go off alone or you will be out flanked and destroyed by smaller, faster tanks. When upgraded the KV-1 becomes practically unstoppable, and only tanks in the same tier and above can kill it. It has a very strong turret, so hiding behind obstacles where only the turret is visible makes this a great defensive tank. It's high health and armor makes it fairly deadly to tier V tanks as its gun can do decent damage that is almost on par with higher tier tanks.