Czech hedgehog

The Czech hedgehog is a static anti-tank obstacle built from metal angle beams or I-beams crossed into a three-dimensional star shape resembling oversized knucklebones, designed to obstruct light and medium tanks and to keep working even after being overturned by an explosion. It was invented by the Czechoslovak officer Major Frantisek Kasik and first deployed along the Czechoslovak-German border in the late 1930s as part of the border fortifications of Czechoslovakia, after early concrete versions proved to shatter into dangerous debris under machine-gun fire and were replaced with metal ones. The Soviet Union used Czech hedgehogs extensively in the Second World War, especially in city fighting where a single obstacle could block a street, Germany incorporated them into the Atlantic Wall, and the military of Ukraine revived mass production of them for city defenses during the 2022 Russian invasion.