The IS-1 is a Heavy Tank and the first of the Soviet Iosif Stalin series, developed in 1943 as a successor to the KV line and initially armed with an 85 mm gun before the IS-2's 122 mm was adopted. It is a tracked vehicle weighing 44 tonnes with a crew of four — driver, gunner, commander, and loader. The V-2IS diesel delivers 520 horsepower for 11.8 hp/t and a maximum speed of 37 km/h.
Main armament is the 85mm D-5S cannon with a coaxial 7.62mm DT-28; the commander has a stabilized 7.62mm DT-28 cupola and the driver a hull 7.62mm DT-28. Sights are 2.5x telescope and periscope with no rangefinder.
This vehicle features a single addon: 100mm Cannon. The 100mm Cannon addon costs 1000 points and replaces the stock 85mm D-5S with the more powerful 100mm D-10T cannon. This modification completely overhauls the vehicle's ammunition suite: the BR-365 APHEBC is replaced by the BR-412B APHEBC, providing an additional 83 mm of maximum penetration (increasing from 135 mm to 218 mm). Furthermore, the O-365K HE shell is replaced by the OF-412, which nearly doubles the explosive mass (from 0.74 kg to 1.46 kg). These improvements in lethality come with the trade-off of a slower reload rate, which increases from 7.84 seconds to 10.5 seconds.
