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, behind the attacking tanks, which were usually IS tanks with equal mobility.