The Soviets were in need of a replacement for the KV-1 and KV-2, so they began a project which ended in the creation of the Object 223 or KV-3. The KV-3 was based on the KV-1 but had a longer chassis. The armor rose up to 130mm and a new conic turret armed with the 107mm ZiS-6 gun was mounted, which is also used on the KV-2/107 and is a very powerful tank gun able to penetrate the armor of any German tank, including the Maus. Only two prototypes were built: the 90 mm armored design with a 76 mm gun (T-150), basically an up-armored KV-1 tank, and a 100 mm armored design with the 85 mm gun (T-220), as the KV-3 turret wasn't ready for production by the outbreak of the war.
In FHSW the tank is a very good opponent to the Tiger tank. His armour gives him a very good protection. The Tiger needs more then one shot in the front armor to destroy a KV-3. Sometimes the shots bounce off. The tank drives a little faster then the KV-2, so in overall the KV-3 is a very strong, fast and powerful battle tank.
With the war underway, the KV factories that were experimenting with prototypes focused on mass production of the KV, the only Soviet tank that was truly feared by Germany at the time. The unfinished prototypes were ripped of their experimental turrets and guns and were sent to the front with KV-1 turrets. This resulted in an interesting "hybrid" of KV-1 with thicker armor and standard armament - KV-220-2 (KV-3) model, which left for the 124th tank battalion on October 16th, 1941 and was destroyed near the Ust-Tosno railway bridge in December 1941.
This vehicle is to be found on Moscow Outskirts on railway station when all flags except last one are under German control.