The IS-1, also known as the Josef Stalin-1, is a Soviet heavy tank developed during World War II as an upgrade to the KV series to address deficiencies in firepower and armor protection. Introduced in late 1943, it featured a sloped hull design, an 85 mm D-5T main gun, and a V2-IS diesel engine producing 520 horsepower, achieving a top speed of about 37 km/h and a range of 150 km. Production was limited to around 200 units before it was quickly superseded by the improved IS-2 in early 1944.

Key Specifications

• Crew : 4 (commander, gunner, loader, driver).

• Weight : Approximately 44 tons.

• Armament : 85 mm D-5T gun (59 rounds) and 7.62 mm DT machine guns (2,520 rounds total).

• Armor : Sloped frontal hull for better deflection, though the lower plate remained vulnerable.

Combat Role and Legacy

The IS-1 was deployed in Soviet guard tank units starting in 1944, primarily for breakthrough operations against German defenses like Panthers and Tigers, but it saw limited success due to its transitional design. It influenced the broader IS tank family, which became crucial in late-war offensives and post- war developments. In modern simulations like War Thunder, the IS-1 is valued for its mobility and gun but criticized for mediocre armor against peers.