Remaining units were deployed to Okinawa in ones and twos for island defense during the Battle of Okinawa, but were severely outnumbered by American artillery. Soviet Union As with the Germans of 1943, most of the Soviet designs mounted anti-tank guns, with limited traverse in casemate-style turretless hulls, in a general design format looking much like the Germans' own Jagdpanzer vehicles. The results were smaller, lighter, and simpler to build weapons that could carry larger guns than any contemporary tank, including the King Tiger. The Soviets produced high numbers of the SU-85 and SU-100 self-propelled guns based on the same chassis as the T-34 medium tank; the heavier-duty powertrain and hull of the IS-2 heavy tank were instead used to produce the heavier-hitting -armed ISU-122 and -armed ISU-152, both of which had impressive anti-tank capabilities earning each of them the Russian nickname Zveroboy ("beast killer") for their ability to destroy German Tigers, Panthers and Elefants. The predecessor of the ISU 152 was the SU-152, built on the KV-1s chassis and shared many similarities (including its gun) with the ISU-152. The ISU-152 built as a heavy assault gun, relied on the weight of the shell fired from its M-1937/43 howitzer to defeat tanks. In 1943, the Soviets also shifted all production of light tanks like the T-70 to much simpler and better-armed SU-76 self-propelled guns, which used the same drive train. The SU-76 was originally designed as an anti-tank vehicle, but was soon relegated to the infantry-support role. United States U.S. Army and counterpart British designs were very different in conception. U.S. doctrine was based, in light of the fall of France, on the perceived need to defeat German blitzkrieg tactics, and U.S. units expected to face large numbers of German tanks, attacking on relatively narrow fronts. These were expected to break through a thin screen of anti-tank guns, hence the decision that the main anti-tank units—the Tank Destroyer (TD) battalions—should be concentrated and very mobile. In practice, such German attacks rarely happened. Throughout the war, only one battalion ever fought in an engagement like that originally envisaged (the 601st, at the Battle of El Guettar). The Tank Destroyer Command eventually numbered over 100,000 men and 80 battalions each equipped with 36 self-propelled tank destroyers or towed guns. Only a few shots were expected to be fired from any firing position. Strong reconnaissance elements were provided so that TDs could use