As a heavy assault gun, the ISU-152 was an extremely valuable weapon in urban combat operations such as the assaults on Berlin, Budapest and Königsberg. The vehicle’s excellent armour protection finally provided the 152.4 mm platform with good protection from most German anti-tank guns, allowing it to advance into the face of direct anti-tank fire, while the huge low-velocity high-explosive rounds were excellent at blasting open even the most heavily fortified and reinforced enemy strongpoints.
Such actions would be much more dangerous and much less effective for a conventional towed artillery piece, with their high crew exposure and low mobility, or even a tank, with their smaller main guns. When supporting tanks, the usual tactics of the ISU-152 were to be used in the second line of the attack order, 100 to 200 metres behind the attacking tanks, which were usually IS tanks with equal mobility.
The ISU-152, like the earlier SU-152 and contemporary ISU-122, was employed by Independent Heavy Self-propelled Artillery Regiments. Between May 1943 and 1945, 53 of these regiments were formed. Many of them were re-formed tank regiments and employed similar direct fire tactics as used by tanks when supporting infantry.
Each of the heavy regiment had 21 guns, divided into four artillery batteries of 5 vehicles and the commander’s vehicle. For support, the heavy regiments had some supplementary unarmoured vehicles such as trucks, jeeps, or motorcycles. In December 1944, Guards Heavy Self-propelled Artillery Brigades were formed, to provide heavy fire support to the tank armies. They were organized along the model of tank brigades, each with 65 ISU-152 or ISU-122 self-propelled guns.
To minimize the risks of being knocked out by Panzerfaust-equipped units during urban operations, the ISU-152 usually acted in one or two vehicle detachments alongside infantry squads for protection. The infantry squad would include a specialist sniper (or at least a sharpshooter), some submachine gunners and sometimes a flamethrower.
The ISU-152’s heavy calibre DShK machinegun was also useful for targeting Panzerfaust gunners hiding on upper floors of city buildings or behind protective cover, barricades, etc. Effective teamwork between the ISU-152 crew and supporting infantry allowed them to achieve their goals with minimal losses, but if such tactics were not adhered to, the attacking vehicles were easily attacked and destroyed, usually through the weaker armor on the roof or rear compartment.