Zimmerit was a paste-like coating used on mid- and late-war German armored fighting vehicles during World War II. It was used to produce a hard layer covering the metal armor of the vehicle, providing enough separation that magnetically attached anti-tank mines would fail to stick to the vehicle, despite Germany being the only country to use magnetic anti-tank mines in numbers. Zimmerit was often left off late-war vehicles due to the unfounded concern that it could catch fire when hit. It was developed by the German company Chemische Werke Zimmer & Co (Berlin). Operation The coating was a barrier that prevented direct contact of magnetic mines with metal surfaces of vehicles. The magnetostatic field decreases very rapidly, with the cube of distance; the non-magnetic coating holds the magnet of the mine too far from the steel of the vehicle for it to adhere. The coating was normally ridged to increase the distance between the magnet and the armor even further, as the high points on the pattern increase the effective thickness of the coating while minimising additional weight. The mixture had the consistency of a thick paste or putty. It was applied to the vehicle, usually at the factory, patterned, and then hardened with blow torches. There were many variations seen in application designs, from the regular ridge-shaped pattern, to a less common waffle-shaped pattern. The differences mostly related to the factory producing each type of AFV. For example, the waffle pattern was seen almost exclusively on Sturmgeschütz III assault guns. In general, vehicles already in service were not coated with Zimmerit. Deployment The German army introduced the Hafthohlladung anti-tank weapon in 1942. This consisted of a shaped charge warhead connected to a ring of metal holding three powerful horseshoe magnets. Issued to infantry, the user would run up to the tank and place the device on any surface to which the magnets would stick. The user would then pull the safety pin and run for safety. The magnets not only held the mine to the vehicle but also provided the correct spacing between warhead and armor, allowing the penetrator jet to form properly. Concerned that the simple design could be easily copied in the USSR or the thought that many of these weapons could fall into the hands of Allied soldiers, the German army began looking for ways to defeat such a weapon when used against their own vehicles.