Comparing: IS vs. Tiger (P)

The IS-1 (IS-85) heavy tank was a thorough modernization of the KV-1. The tank featured the 85-mm D-5T gun. The IS-1 entered mass production in October 1943, but work was discontinued at the beginning of 1944, as the IS-2 (IS-122) tank entered mass production in December 1943. A total of 107 vehicles were manufactured.

On May 26, 1941, Adolf Hitler ordered Ferdinand Porsche and the Henschel company to develop prototypes of a new heavy tank. The prototypes were shown to the Führer on April 20, 1942. Manufacturing began, but the production run was cut short due to the complexity of the tank's drive and control systems, and a shortage of the required copper. Later, 90 produced hulls were converted into Ferdinand tank destroyers.