caltrops

Caltrops are a form of area-denial weapon, a low-tech alternative to land mines.
Each caltrop is a small object with multiple sharp prongs oriented in different directions, usually in a tetrahedral configuration, so that when dropped loosely on the ground one prong always points up.
When scattered in large numbers over a given area they serve to delay an advancing army by inflicting foot injuries and infections to soldiers, horses and support animals, being particularly effective against camels.
In modern times they may also be designed to cause flat tires in wheeled vehicles.

See also

• makibishi: Traditional Japanese caltrops.