A caltrop (calthrop, jack rock, star nail) is a weapon made up of four (or 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). Caltrops serve to slow down the advance of horses, war elephants, and human troops. It was said to be particularly effective against the soft feet of camels. In more modern times, caltrops could be effective against wheeled vehicles. In Japan such devices were known as makibishi.

The device shares its name with the caltrop, Tribulus terrestris (Zygophyllaceae), whose spiked seed case can also injure feet and puncture tires. Compare also the Star thistle, Centaurea calcitrapa, whose Latin name calcitrapa means "foot trap".

History

The caltrop has been known since ancient times and was known to the Romans as tribulus or sometimes as Murex ferreus, the latter meaning 'jagged iron'.

The late Roman writer Vegetius, in his work De Re Militari, wrote:

The armed chariots used in war by Antiochus and Mithridates at first terrified the Romans, but they afterwards made a jest of them. As a chariot of this sort does not always meet with plain and level ground, the least obstruction stops it. And if one of the horses be either killed or wounded, it falls into the enemy's hands. The Roman soldiers rendered them useless chiefly by the following contrivance: at the instant the engagement began, they strewed the field of battle with caltrops, and the horses that drew the chariots, running full speed on them, were infallibly destroyed. A caltrop is a machine composed of four spikes or points arranged so that in whatever manner it is thrown on the ground, it rests on three and presents the fourth upright.

The caltrop continued in use into the 17th century, a single example was found in Jamestown, Virginia in the USA.

Undoubtedly the most unusual weapon or military device surviving from seventeenth-century Virginia is known as a caltrop, a single example of which has been found at Jamestown. It amounts to a widely spread iron tripod about three inches long with another leg sticking vertically upward, so that however you throw it down, one spike always sticks up. ... There is no doubt that the most inscrutable Indian treading on a caltrop would be shocked into noisy comment. ... The fact that only one has been found would seem to suggest that they were used little, if at all. As with all military equipment designed for European wars, the caltrop’s presence in Virginia must be considered in the light of possible attacks by the Spaniards as well as assaults from the Indians.American Heritage.com link broken as of 2006-03-04

Caltrop-like devices

Punji sticks perform a similar role to caltrops. These are sharpened sticks placed vertically in the ground. Their use in modern times target the body and limbs of a falling victim rather than well shod feet, by means of a pit or tripwire.

In Britain, during the Second World War, large caltrop shaped objects made from reinforced concrete were used as anti-tank devices; although it seems that these were rare. Very much more common, were concrete devices called dragon's teeth that designed to wedge into tank treads. However, dragon's teeth are immobile, so the analogy with the caltrop is inexact. Another caltrop-like WWII defence is the massive, steel, freestanding Czech hedgehogs that were designed to damage ships and landing craft.

The caltrop is the symbol of the US Army's III Corps, which is based at Fort Hood, Texas. III Corps traces its lineage to the days of horse cavalry, which used the caltrop as an area-denial weapon. Fort Hood is the only installation in the US Army that has declared the caltrop to be a weapon prohibited in the barracks.

Modern Uses

Labor activists

Caltrops have been used at times during labor strikes and other disputes. Such devices were used by some to destroy the tires of management and replacement workers.

Because of the prevalence of caltrops during the Caterpillar strike of the mid-1990s, the state of Illinois passed a law making the possession of such devices a misdemeanor.

Environmental activists

In the 1970s, activists in the United States deployed caltrops against the tires of logging trucks. Earth First! quickly condemned the practice, seeing it as a hazard to humans and animals.

Criminals

Caltrops have been used by criminals in some countries to hinder pursuing police cars, especially in Sweden where they have become "standard procedure" at robberies of valuable transports.

Other usages

In role-playing games, some players refer to 4-sided dice as "caltrops" because, like a caltrop, their tetrahedral design guarantees that they will land with one point facing up. When stepped on with bare feet, plenty of pain will result.

Students sometimes play practical jokes by twisting staples together to form a mini-caltrop, then placing it on a hard seat where the victim will sit on it. Such devices are often referred to as "ass scorpions" or "seat tacks".

See also

• abatis
• cheval de frise
• medieval fortification
• trou de loup
• water caltrop, a plant

References