A caltrop is a device—usually made out of metal—with four spikes arranged in such a way that when any three spikes rest on the ground, the fourth points upward. They come in all shapes and sizes—from Christmas tree caltrops with jagged edges to caltrops comprised of hollow spikes.

Caltrops are very useful in slowing the advance of troops attacking by vehicle or animal—horses, camels, and war elephants.

The weapon got its name from the star thistle, a weed with a form and function similar to its namesake.

 
Intelligence Uses

During World War II, caltrops were used extensively for Jedburgh team operations. The Jedburgh teams were created in the early days of the Office of Strategic Services—the predecessor of today’s CIA. The teams of American, British and French officers would parachute into enemy-occupied territory to conduct sabotage. The Jedburghs scattered caltrops across enemy aircraft runways. These caltrops were made out of hollow spikes, which could puncture a self-sealing tire and cause it to blow out. When a fighter plane rolled over a caltrop during take off or landing, the tires would blow out, causing the plane to go into an uncontrollable ground loop and eventually crash.

In more recent examples, caltrops were used during the Korean War. The United Nations used caltrops against the sneaker-clad Chinese troops.

Today, caltrops are particularly effective when strewn across enemy roadways or airport runways.

 
History

Caltrops have been used throughout history in Europe, Asia, North Africa and the New World. However, caltrops are often overlooked in favor of more impressive warfare weaponry, such as bombs or poison gas. The unfortunate soul who stumbles across a caltrop during battle has healthy fear and respect for the silent weapon. When encountered, a caltrop can easily puncture pneumatic tires and gravely injure—and sometimes kill—soldiers or animals.

A caltrop could be considered the ideal weapon because they:

    * Are cheap and easy to make,
    * Portable,
    * Retrievable and reusable,
    * Extremely effective,
    * Require no skill or training to use, and
    * No maintenance or special care.

Macedonia
Caltrops were used as early as 331 B.C. at the Battle of Arbela—or Gaugamela—in what was once Persia. The Persians sowed caltrops across the battlefield to restrict Macedonian troop movement. When horses pulling chariots happened across a caltrop at full speed, the chariots were damaged and the horses were gravely injured. Despite the obstacle created by the caltrops, Alexander the Great of Macedonia was able to navigate through the caltrops and win this battle. He recognized the caltrop’s worth as a weapon and used them against other enemies.

Roman Empire
The Romans adopted the caltrop from their encounters with Hellenistic armies. During the Battle of Nisibis fought in A.D. 217 in what is now southern Turkey, the Romans employed the caltrops in an ingenious manner. The Romans faked a retreat and dumped caltrops—which quickly sank into the sand—behind them. As the Parthians followed, horses and camels ran over the caltrops and were made lame, throwing their riders to the ground. The battle lasted for three days and ended in a draw between the two armies.

Asia
Genghis Kahn encountered caltrops during the Mongol invasions in 1213 when he attempted to attack the main fortress of the Chin Empire. The land surrounding the fort was littered with caltrops. After camping out near the fort for nearly a month, Genghis Kahn decided to move on to his next target rather than risk falling victim to a caltrop.

Europe
The Scots also used caltrops against the British during the Battle of Bannockburn fought near Stirling, Scotland, in 1314. The Scottish army placed nail caltrops on the battlefield, which ultimately halted the English cavalry and resulted in a British retreat. Historians say that the use of the caltrop during this battle contributed to the Scottish victory.

New World
Caltrops continued to be used into the 17th century. A caltrop was found in Jamestown during an archaeological dig. The English settlers probably used caltrops to discourage surprise attacks by native Americans.

From the early Roman Empire to the Cold War, the caltrop has stood the test of time as a useful weapon.

The CIA Museum currently has a caltrop on display in the Directorate of Science and Technology exhibit.