Anti-tank defense proper was by 1942 designed in First World War fashion with several prepared trench lines incorporating anti-tank weapons of different capabilities. Depending on terrain and the available line-of-sight, the longer-ranged guns could begin to fire on approaching tanks from as far as 2 kilometers, which was also the range at which German Panther and Tiger tank gunners were trained to fire. Anti-tank guns were usually deployed to cover terrain more suitable for tanks, and were protected by minefields laid at about 500 meters to 1 kilometer from their positions by combat engineers. In the Red Army the anti-tank rifle units would be positioned throughout the forward trench line and would engage the lighter tanks and any other vehicles, such as infantry half-tracks in an attempt to separate them from the tanks. The anti-tank guns deployed further back would often hold their fire until enemy tanks were within the most effective range for their ammunition. Where there were insufficient anti-tank weapons, engineers would construct anti-tank obstacles such as dragon's teeth or czech hedgehog.