 Subsequently, high explosives were developed and used in land mines.Some fortifications in the Roman Empire were surrounded by a series of hazards buried in the ground.These included "goads", foot-long pieces of wood with iron hooks on their ends; "lilia" (lilies, so named after their appearance), which were pits in which sharpened logs were arranged in a five-point pattern; and "abatis", fallen trees with sharpened branches facing outwards.