CROWSFEET. Properly known as caltrops, crowsfeet are small metal spikes cast so that their four points form a tetrahedron. According to Captain George Smith's Military Dictionary, a caltrop is "a piece of iron having four points, all disposed in a triangular form, so that three of them always rest upon the ground and the fourth stands upwards in a perpendicular direction. Each point is three or four inches long." Dropped at random, their shape ensures that they will always have one point straight up. They are of ancient origin, developed to be scattered in the path of cavalry. In modern war, they can still be used as a passive device to puncture pneumatic tires. When the British evacuated Boston by sea in 1776 they sprinkled caltrops of a different design on the last mile of the road from Roxbury into the city to slow the American advance. According to James Thacher, "the implement consists of an iron ball armed with four sharp points about one inch in length, so formed that which way soever it may fall one point still lies upwards to pierce the feet of horses or men."
Smith, George. Military Dictionary. London, 1779
Thacher, James. Military Journal during the American Revolutionary War. Boston, 1823.
revised by Harold E. Selesky