The designs followed on from the more lightly armored ("tank hunter") designs, which took an anti-tank gun and mounted it on top of a tank chassis with supplementary armor fitted around the gun crew. However, the armor typically had an open rear and top, almost never providing the crew with full protection from the elements. In addition, much experience was gained from the series of
assault guns for infantry support, which already used heavily armored casemates, completely enclosing the vehicle's crew. Although they were associated with artillery and infantry support, they were often used in the anti-tank role. ==Tactical use==