A caltrop (also known as caltrap, galtrop, cheval trap, galthrap,[1]galtrap, calthrop, jackrock or crow's foot[2][3]) is an area denial weapon made up of usually four, but possibly more, sharp nails or spines arranged in such a manner that one of them always points upward from a stable base (for example, a tetrahedron). Historically, caltrops were part of defences that served to slow the advance of troops, especially horses, chariots, and war elephants, and were particularly effective against the soft feet of camels.[4] In modern times, caltrops are effective when used against wheeled vehicles with pneumatic tires.[5]
^Battle of Alesia (Caesar's conquest of Gaul in 52 BC), Battlefield Detectives program, (2006), rebroadcast: 2008-09-08 on History Channel International (13:00-14:00 hrs EDST); Note: No mention of name caltrop at all, but illustrated and given as battle key to defend Roman lines of circumvallation per recent digs evidence.
^Robert W. Reid (1 September 2006). "The Caltrop: A weapon that's barely changed over 2,300 years". HistoryNet. Retrieved 2023-06-24. Today, it has reclaimed its old Greek name and reappeared as the tetrahedron, the bane of all vehicles running on pneumatic tires, and is used by both the military and police.