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Caltrops of WWI

Watch Your Step! Don’t Tread on the Caltrop, A Weapon with a Pointed History


There is a cunning and deadly device that used by armies in the past, and up to the present day. It’s a weapon mostly overlooked but is yet brilliantly effective—the caltrop. The caltrop (or calthrop) is a crude, cheap, iron ball with spikes. It is an anti-personal weapon used to slow down troops on foot, horses, war elephants, and even tires on small vehicles. Bigger versions were used against tanks and water landing craft.

Caltrops came with three prongs, or even four, and to use the weapon required no skill at all, other than watching where you stepped once you placed it! Simply scatter in the vicinity of your intended host, and they’ll find it. Once the enemy marched over them, great yowls of anguish could be heard. Stepping on one could cause a nasty puncture-wound for the enemy marching or to the cavalry accompanying them, which could lead to infection or death if not treated hastily.

Designed by Nature, Employed by Man

The name caltrop is said to mean “star thistle,” which is said to be a weed whose spikey seeds performed similarly to the weapon itself, painfully piercing deeply into the feet of careless pedestrians. The Greeks called it “tribolos” due to its shape. The Romans called it “tribulus” but it was called “murex” as well, for it looked like the shell of a mollusk.

Thumbtack-like Tribulus terrestris nutlets are a hazard to bicycle tires, feet, and ancient armies.

Thumbtack-like Tribulus terrestris nutlets are a hazard to bicycle tires, feet, and ancient armies. (Public Domain)

The origins of the weapon are a mystery. However, some have pointed out that the first use of the weapon was at the Battle of Arbela (also known as the Battle of Gaugamela) in 331 BCE.

Watch your step! Darius’ flight at The Battle of Gaugamela

Watch your step! Darius’ flight at The Battle of Gaugamela (detail) (Luis García /CC BY-SA 3.0)

The Macedonian author Polyaenus wrote about the event 500 years later, making the claim that Darius III placed many of these small nasty devices in front of his army to deter the oncoming forces of Alexander the Great. Nevertheless, Alexander was able to maneuver around this obstacle, making his way through the Persian lines, and thus winning the battle. As for that being the first time the weapon was used, that cannot be confirmed, but it should be noted that Polyaenus does not mention this device as new, and the passage in question suggests that the Macedonian army must have been familiar with the weapon.

When Alexander the Great died, the caltrop became a fan favorite among his various Hellenistic successors who battled for the throne of Alexander. Many of the caltrops at the time were made of wood with metal spikes and is said they were used very extensively in battle and were deployed long before the battle was to take place. It is also mentioned that sometimes there was just too many of them! Such that the army that deployed them restricted their own movement in battle. So, they were very effective against enemy infantry and cavalry— including those who placed them there in the first place.

Julius Caesar Seizes the Caltrop, Changes it to his Advantage

Besides the Hellenistic monarchs who used and abused the device, the Romans also adopted this practical weapon and made it as flexible as the army that deployed them. However, the Romans made a slight change to the caltrop. During the siege of Alesia in 52 BCE, Julius Caesar took the caltrop concept and remade it into something that fit his needs. Instead of a ball with spikes, he took the spike concept, placed them in wooden blocks, and thus they became known as “goads”. Just as effective as the caltrop, the goad would serve the same practicality as the caltrop, and quite possibly may have been cheaper to build.

Roman caltrop at Westfälisches Museum für Archäologie, Herne, Germany

Roman caltrop at Westfälisches Museum für Archäologie, Herne, Germany (Bullenwächter/CC BY-SA 3.0)

The Roman writer Vegetius mentions their use against chariots:

“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”…


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Cam Rea is an author and military historian. He has written numerous articles for Ancient Origins, Classical Wisdom Weekly, and has authored several books, including: Leviathan vs. Behemoth: The Roman-Parthian Wars 66 BC-217 AD


Top Image: Caltrops of WWI. (Tangopaso/Public Domain);Deriv

By Cam Rea



How can a 3-prong caltrop work? I think they are always 4-pronged. With a 4-prong, there are always 3 points on the ground and one pointed up. With a 3-prong, all the points would be on the ground, or so it seems to me.

Cam Rea's picture

Cam Rea

Cam Rea is a Military Historian and currently the Associate Editor/Writer at Strategy & Tactics Press. Mr. Rea has published several books and written numerous articles for Strategy & Tactics Press and Classical Wisdom Weekly. His most current publication is... Read More

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