IS tank family

The IS tanks (Russian: ИС) were a series of heavy tanks developed as a successor to the KV-series by the Soviet Union during World War II. The IS acronym is the anglicized initialism of Joseph Stalin (Ио́сиф Ста́лин, Iosif Stalin). The heavy tanks were designed as a response to the capture of a German Tiger I in 1943. They were mainly designed as breakthrough tanks, firing a heavy high-explosive shell that was useful against entrenchments and bunkers. The IS-2 went into service in April 1944 and was used as a spearhead by the Red Army in the final stage of the Battle of Berlin. The IS-3 served on the Chinese-Soviet border, the Hungarian Revolution, the Prague Spring and on both sides of the Six-Day War. The series eventually culminated in the T-10 heavy tank.
The KV-85 was a KV-1S with the new turret from the Object 237 (IS-85) still in development, mounting the 85mm D-5T gun. The tank was a result of the USSR's tank design bureau being torn in two, one half focusing on the KV-85 and its variants, and the other working on the later IS series. The IS-85 was soon finished and it combined the hull of the KV-13, the new turret from the KV-85, and the same 85mm D-5T gun as both these tanks. The IS-85 was later referred to as IS-1. The first IS-1 rolled off the line in October 1943, but production was stopped in January 1944, as the IS-1 was quickly replaced by the IS-2. Because of this, only about 200 IS-1s were produced.
In December 1943, two up-gunned variants of the IS-85 were created: the IS-100, armed with the 100mm BS-3 gun, and the IS-122, armed with the 122mm A19 gun (later adopted and renamed as the D-25T). The IS-122 was found to be better than the IS-100 in trials, and so the IS-100 was dropped. The IS-122 was renamed to IS-2 and production started with the 1943 model using a KV-13 chassis. First deliveries of IS-2s were in December 1943. The 1944 model was produced with a revised front slope that was better from an armor point of view while still saving weight. Production in bulk of the IS-2 started in February 1944 and ended nearing the end of World War II. By the end of World War II, 3,854 IS-2 model 1943 and model 1944's combined had been produced. German general Hasso von Manteuffel, who met tanks of that series in combat for the first time in Romania in 1944, considered the Stalin tank "the finest in the world."
There are two tanks known as IS-3: Object 244 was an IS-2 rearmed with the long-barrelled 85 mm cannon (D-5T-85-BM) and developed by the Leningrad Kirov Plant (LKZ), which was never series-produced for service use.
The IS-3 known as Object 703 is a Soviet heavy tank developed in late 1944, and began production in May 1945. Its semi-hemispherical cast turret (resembling an upturned soup bowl), became the hallmark of post-war Soviet tanks. Its pike nose design was also mirrored by other tanks of the IS tank family such as the IS-7 and T-10 tank. Too late to see combat in World War II, the IS-3 participated in the Berlin Victory Parade of 1945, and on the Chinese-Soviet border, the Soviet invasion of Hungary, the Prague Spring and the Six-Day War.
There are two tanks known as IS-4: Object 245 and Object 701. Object 245 was an IS-2 rearmed with a long 100 mm D-10T cannon.
The IS-4 known as the Object 701 was a Soviet heavy tank that started development in 1943 and began production in 1946. Derived from the IS-2 and part of the IS tank family the IS-4 featured a longer hull and increased armor. With the IS-3 already in production, and when sluggish mobility and decreased need for tanks (particularly heavy tanks) became an issue, many were sent to the Russian Far East with some eventually becoming pillboxes along the Chinese border in the 1960s. Less than 250 were produced.
The IS-5, is merely one of the many designations given to what would ultimately become the T-10 tank.
There existed two different IS-6s: the Object 253 was an attempt to develop a practical electrical transmission system for heavy tanks. Similar systems had been tested previously in France and the United States and had been used with limited success in the German Elefant/Ferdinand tank destroyer during World War II. The experimental transmission proved unreliable and was dangerously prone to overheating, and development was discontinued. The alternative Object 252 shared the same hull and turret as the Object 253, but used a different suspension with no return rollers, and a conventional mechanical transmission. The design was deemed to offer no significant advantages over the IS-2, just the reload time was less, and the IS-6 project was halted.
Since the IS-6 proved to have no significant advantages over IS-2 and its rival IS-4, in November 1944, they decided to dramatically upgrade the tank. The project was called "Object 252U" (U stands for "Improvement" in Russian). The tank featured a heavily sloped pike-nose armor, a new 122 mm D-13T gun, and more slope on the sides and rear. The design proved to be problematic in terms of crew comfort since the interior was too cramped and the design was cancelled.
The IS-7 heavy tank design began in Leningrad in 1945 by Nikolai Fedorovich Shashmurin and was developed in 1948. Weighing 68 tonnes, thickly armoured and armed with a 130 mm S-70 long-barrelled gun, it was the largest and heaviest member of the IS family.
The IS-8 (also known as Objekt 730) was the final development of the KV and IS tank series. It was accepted into service in 1952 as the IS-8, but due to the political climate in the wake of Stalin's death in 1953, it was renamed T-10, as it was the tenth heavy tank in Soviet service.
The biggest differences from its direct ancestor, the IS-3, were a longer hull, seven pairs of road wheels instead of six, a larger turret mounting a new gun with fume extractor, an improved diesel engine, and increased armour. General performance was similar, although the T-10 could carry more ammunition.
T-10s (like the earlier tanks they replaced) were deployed in independent tank regiments belonging to armies, and independent tank battalions belonging to divisions. These independent tank units could be attached to mechanized units, to support infantry operations and perform breakthroughs.
The T-10M is the final iteration of this type. It featured a longer gun barrel than previous models with 5-baffle muzzle brake and 14.5 mm machine gun. This was the last Soviet heavy tank to enter service. When the advanced T-64 MBT became available it replaced the T-10 in front line formations.
The IS-2 entered combat in World War II during the first months of 1944. The Soviets produced significant numbers of the type (close to 4,000) and deployed them against the most advanced German designs of the time, notably the Tiger I, Tiger II, and Panther, as well as against Elefant tank destroyers. The IS-2 was best used for bunker assault using its high-explosive ammunition, as its reload rate, just 2 rounds per minute, made it ineffective as a tank destroyer. The IS-3 saw service on the Chinese-Soviet border, the Soviet invasion of Hungary, the Prague Spring and on both sides of the Six-Day War. However, the mobility and firepower of medium-tanks and the evolution of the main battle tank rendered heavy tanks obsolete.
There are several surviving IS series tanks, with examples found at the following: