Of these tank destroyers, only the gun of the M36 proved effective against the frontal armor of Germans' larger armored vehicles at long range. The open top and light armor made these tank destroyers vulnerable to anything greater than small-arms fire. As the number of German tanks encountered by American forces steadily decreased throughout the war, most battalions were split up and assigned to infantry units as supporting arms, fighting as assault guns or being used essentially as tanks. In this sense they were an alternative to the Independent tank battalions that were attached to various Infantry Divisions.