The ISU-152 was a further development of the SU-152 Assault Howitzer, but based on the IS tank’s (Iosef Stalin) lower chassis and running gear instead of the KV tank’s (KV from the prewar defense minister, Klimenti Voroshilov). Although the ISU-152 mounted the same 152mm M1937/43 (ML-20S) gun-howitzer of the SU-152, the new crew compartment was now higher (as the IS chassis was not as deep as the KV) and more rectangular. The old circular KV hatches were replaced with the SU-100 style cupolas and new standard periscopes installed in each. The new ISU 152, and the similar ISU-122 (fitted with a 122mm A-19 cannon), were first produced at Chelyabinsk during late 1943 at the same time as the IS-1 heavy tanks.
The success of the SU-152, coupled with the development of the IS (losef Stalin) heavy tank hull, led the NKTP to order design teams at Chelyabinsk, in cooperation the Mechanized Artillery Bureau (BAS) and General F. Petrov, to design two new heavy assault guns based on the IS-2 tank’s hull and chassis. The initial vehicle, designated Object 241, or ISU249, was similar to the SU-152, except for a higher superstructure and more rectangular with less sloped side armour. Thicker frontal and side armour (90mm/3.54in compared to 60mm/2.36in on the SU-152) meant that the internal area of both vehicles was the same, with storage for only 20 rounds each for the 152mm (5.98in) ML-20 howitzer gun. The main difference between the SU-152 and ISU series of vehicles was a lower suspension and a new, heavy two-piece gun mantlet bolted onto the right-hand side of the hull. Re-classified as ISU-152, production began at the end of 1943.
The appearance of the immensely powerful Panzerkampfwagen King Tiger in fighting south of Warsaw in August 1944 led to a number of plans to up-gun both types of ISU with the new 122mm (4.8in) BR-7 and 152mm (5.98in) BR-8 long-barrelled guns, but the realization that the Germans could not deploy the Royal Tiger in significant numbers caused production of these prototypes to be abandoned. Another reason was the conclusion of Soviet technicians, based on combat results, that the IS-2 tank could deal with this new threat.
Post-war changes were made to the final production run of ISU-152Ks by using the IS-2m chassis and the IS-3 engine deck. A total of 4075 ISU-152s were produced during the war, and a further 2450 manufactured between 1945 and 1947, when production ceased.
The heavy SU regiments were originally equipped with the SU-152, a 152mm howitzer mounted on a KV-1S chassis. The first 25 of them were rushed into service in time for the Battle of Kursk, where the effect of their 100 pound shells on German Panthers and Tigers earned them the nickname ‘Zvierboi’ (‘Big Game Hunters’). The SU-152 was only in production during 1943, and 670 were built. They were increasingly replaced in 1944 by two heavy SUs on the chassis of the new IS-II tank: the ISU-152, which was built until 1947.
The Soviets used term “Shturmovaya Artilleriiskaya Ustanovka” (Assault Gun) for the SU-122, SU-152, ISU-152, ISU-122.
When the ISU- 122/152 heavy self-propelled artillery regiments were originally formed in February of 1944, the vehicles were placed in groups of 21 assault guns with four batteries per regiment. The SP guns were intended to support offensive breakthrough operations and expected to deal with German strong points and anti-tank defenses from long distances. First deployed during the summer of ’44 offensive “Bagration”, the ISU-122/152 regiments took part in what was probably the largest concentration of Soviet armor up to that time and proved themselves to be very useful AFVs. After WWII the construction of these assault vehicles continued and they were sold to other Warsaw Pact member countries as well as Algeria, Egypt and China.
This Soviet News photo illustrates the internal hatch detail of both the gunner’s on the left and the commander’s split hatches. The hatch half with the periscope closes first and the second half then slightly over laps the first and has two small latches at its edge to hold the hatch in place. Normally there was a leather covered pull chain connecting these latches (as seen on the gunner’s hatch) and a simple pull on the strap would release both latches so you could open the hatch from the inside. The commander here appears to be holding his cloth tanker’s helmet in his left hand while the right rests on the long handle of his periscope. Notice the antenna base, just forward of his hatch, and also the domed armor cover over the hull fan, located directly between the two hatches.
The early ISU-152M was updated to the last version in 1956, adding more ammo storage to the new K model for a total of 30 rounds, most of the additional rounds being stored in a third rack on the left side of the hull. Also added to the ISU-152K was a new TPKU ranging sight on the commander’s cupola and an improved PS-10 telescopic sight for the gunner, as well as a revised engine and cooling system.