Caltrop is a type of defensive obstacle used to stop enemy cavalry.

The Romans called this device “tribolus, ” and the Japanese — “makibishi.”

This obstacle consisted of four sharp metal spikes pointing in different directions. Some spikes were equipped with additional hooks. Caltrops were scattered along the route or advance of the enemy cavalry. Caltrops were also effectively used against infantry, camels and even war elephants.

The design of a caltrop ensured that one of the spikes would always be pointing upwards, while the other three provided the stability of the object.

To be effective, a large number of such spikes were scattered over an area, with at least three per square meter. The depth of such a field ranged from 100 to 150 meters, depending on the needs and conditions of the combat mission.

Due to its small size, caltrops were almost invisible in the grass. The infantry formation attacking would be disrupted when soldiers slowed down to avoid injuring their feet.

Researchers have not yet been able to determine who and where invented this type of defensive obstacle. Some believe that caltrops appeared in China, others talk about Rome or Greece, and still others mention Ancient Rus, where this device was used to fight the nomads of the Golden Horde.

There are mentions of finds that are similar to a caltrop, but made of bone. They were discovered during archaeological excavations in Crimea and date back to the 5th century BCE. There are also accounts confirming the use of iron caltrops by Alexander the Great in the Battle of Gaugamela in 331 BCE.

This type of obstacle was effectively used in 1609 in the defense of the Trinity Lavra of St. Sergius against the Polish-Lithuanian cavalry.

Subsequently, caltrops were used in nearly all wars up to the 20th century. For example, in the Battle of Borodino, the Russian army employed more than a thousand tons of caltrops. Nowadays, devices similar to caltrops are used mainly as anti-vehicle barriers, designed to puncture tires.