Attention to camouflage, quick relocation between firing positions, and massed ambushes of four or five vehicles firing in salvo at a single target's flanks reduced the disadvantage of the low rate of fire. Self-propelled artillery The ISU-152 was also sometimes used as self-propelled artillery for support on the battlefield and preparatory bombardments, though it had a medium range of fire and a slow speed of reloading. The Soviet army had not developed specialized vehicles for this purpose. Their tank and mechanized units were well equipped with towed artillery, but the towed guns were very vulnerable while moving and they could not support tanks and motorized infantry during rapid advances into enemy positions, especially when they lacked the armored fully enclosed design of vehicles like ISU-152. The internal stowage was limited to only 20 or 21 rounds of ammunition, with extra rounds often stowed on the rear deck. Replenishing the vehicle's ammunition supply took over 40 minutes and required a very strong loader, due to the large size and weight of the shells - over . The ST-10 telescopic sight used for direct fire was graduated up to . A second, panoramic, sight was used for direct fire up to range no direct fire. However, it was problematic for the gunner to switch between the two. To compensate it was simpler to concentrate the fire of several vehicles onto the target, sacrificing accuracy for volume of firepower. The high-explosive shells were large enough to take out even a heavily armoured vehicle, or a fortification with the even heavier long-range concrete-piercing shells. The usual complement of ammunition was 13 high-explosive and 7 armour-piercing or concrete-piercing. The armor penetration can vary between ammunition batches and different rolled homogeneous armour. Soviet military service World War II Eastern Front Continuation War Soviet–Japanese War Manchurian Invasion Hungarian Revolution Foreign military service Finland In June 1944, during the Continuation War, a captured ISU-152 was used by the Finnish military. It was abandoned during the counter-attack at Kärstilänjärvi after receiving numerous shots from Soviet T-34-85 medium tanks. This was a direct result of the Finnish crew's lack of experience and training with the ISU-152. Another captured one was repaired in Varkaus, Finland, but never saw combat. Poland In 1944, more than 30 ISU-152s were delivered to the People's Army of Poland. Shortly afterwards, the Polish military created the 25th Polish Self-Propelled Artillery Regiment, which consisted of 10 ISU-152s