Caltrop

A caltrop (en; also known as caltrap, galtrop, cheval trap, galthrap,[1] galtrap, calthrop, jackrock or crow's foot[2][3]) is an area denial weapon made up of usually four, but possibly 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). Historically, caltrops were part of defences that served to slow the advance of troops, especially horses, chariots, and war elephants, and were particularly effective against the soft feet of camels.[4] In modern times, caltrops are effective when used against wheeled vehicles with pneumatic tires.[5]

## Contents

* 1 Name
* 2 History
* 3 Modern uses
* 3.1 World War I
* 3.2 World War II
* 3.3 Tire deflation device
* 3.4 Labour disputes
* 3.5 Via drones
* 4 Symbol
* 5 Similar devices
* 6 See also
* 7 Footnotes
* 8 References

## Name

The modern name "caltrop" is derived from the Old English calcatrippe (heel-trap),[6][7] such as in the French usage chausse-trape (shoe-trap). The Latin word tribulus originally referred to this and provides the generic name of a plant commonly called the caltrop, Tribulus terrestris, whose spiked seed cases resemble caltrops and can injure feet and puncture bicycle tires.[8] This plant can be compared to Centaurea calcitrapa, which is sometimes called the "caltrop".[9] Trapa natans, a water plant with similarly shaped spiked seeds and edible fruit, is called the "water caltrop".[10]

## History

File:Three Kingdoms Shu Bronze Caltrops (40512948263).jpgBronze caltrops from the Three Kingdoms era A 16th-century caltrop Illustration from the 18th-century Chinese book Gujin Tushu Jicheng, showing caltrops with spikes that stick in the ground

The caltrop was called tribulus[11] by the ancient Romans, or sometimes murex ferreus,[12] the latter meaning "jagged iron" (literally "iron spiny snail-shell"). The former term derives from the ancient Greek word tribolos meaning three spikes.[13]

The late Roman writer Vegetius, referring in his work De re militari to scythed chariots, wrote:[14]

> 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 device 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.

Another example of the use of caltrops was found in Jamestown, Virginia, in the United States:[15]

> 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. ... 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.

In China, caltrop is called Jili(蒺藜) and comes in different shapes and materials. It is thrown on the ground to stop people and horses, and sometimes it is coated with poison. Some styles are also called Jizhuading(雞爪釘) because they resemble chicken claws.

The Japanese version of the caltrop is called makibishi. Makibishi were sharp spiked objects that were used in feudal Japan to slow pursuers and also were used in the defence of samurai fortifications. Iron makibishi were called tetsubishi, while the makibishi made from the dried seed pod of the water caltrop, or water chestnut (genus Trapa), formed a natural type of makibashi called tennenbishi. Both types of makibishi could penetrate the thin soles of shoes, such as the waraji sandals, which were commonly worn in feudal Japan.[16][17]

As a protective measure and countermeasure, European late medieval military engineers proposed iron soles that could be strapped under shoes like pattens to protect the feet from hidden traps.[18]

* Traditional caltrops and mines from the Mongol Empire

## Modern uses

Crow's feet boards studded with spikes. These were laid on the ground to prevent the enemy from approaching the defences. This board was used by the Russian Army during the Battle of Balaclava. On display at Royal Engineers Museum, Kent.

### World War I

### World War II

Caltrops were used extensively and effectively during World War II. The modifications and variants produced by the Special Operations Executive (SOE) and the Office of Strategic Services (OSS) of the United States[19] are still in use today within special forces and law enforcement bodies.[who?]

The Germans dropped crow's feet (German: Krähenfüße).[20] These were made from two segments of sheet metal welded together into a tetrapod with four barbed points and then painted in camouflage colours. They came in two sizes with a side length of either 65 or 75 millimetres (2.6 or 3.0 in). They were dropped from aircraft in containers the same size as 500 kg (1,100 lb) bombs and were dispersed by a small explosive charge.[20][21]

### Tire deflation device

See also: Engineering:Spike strip

Caltrop used by the US Office of Strategic Services. The hollow spikes puncture self-sealing rubber tires. The hole in the center allows air to escape even if other ends of the tube are sealed by soft ground.

Inventors patented caltrop-like devices to deflate vehicle tires in a manner useful to law enforcement agencies or the military.[22][23] They are currently used by the military and police.[5]

### Labour disputes

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

Caltrops, referred to as "jack rocks" in news articles, were used during the Caterpillar strike in 1995, puncturing tires on vehicles crossing the picket line in Peoria, Illinois. Because of their small size and the difficulty proving their source, both the company and the United Auto Workers blamed each other. Collateral damage included a school bus and a walking mail carrier.[24] In Illinois, the state legislature passed a law making the possession of such devices a misdemeanor.[25]

### Via drones

During the Russian invasion of Ukraine, Ukraine has used drones to drop caltrops on key roads to disrupt wheeled vehicles carrying Russian military materiel, and make them easier to target with loitering munitions.[26]

## Symbol

A caltrop has a variety of symbolic uses and is commonly found as a charge in heraldry.[27] For instance, the Finnish noble family Fotangel (Swedish for 'caltrop') had arms gules, three caltrops argent.

* Coat of arms of Stirling

* Shoulder insignia of III Corps (United States)

* 3rd Marine Division (United States)

## Similar devices

File:Rozsochac.JPGCzech hedgehogs deployed at the Stachelberg fortress in Czechoslovakia in 1938

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.[28] Much more common were concrete devices called dragon's teeth, which were designed to wedge into tank treads. Large ones weighing over 1 tonne (1.1 tons) are still used defensively to deny access to wheeled vehicles, especially in camp areas. Because dragon's teeth are immobile, the analogy with the caltrop is inexact. Another caltrop-like defence during World War II was the massive steel, freestanding Czech hedgehog; the works were designed as anti-tank obstacles and could also damage landing craft and warships that came too close to shore. These were used by the Germans to defend beaches in Normandy and other coastal areas.[29] Czech hedgehogs are heavily featured and plainly visible in the 1998 Steven Spielberg-directed American epic war film Saving Private Ryan, throughout the scenes early in the film depicting the June 6, 1944 Omaha Beach assault (part of the Normandy landings during World War II).

## See also

* Booby trap
* Knucklebones, a game, with similar hazards
* Triskelion

## Footnotes

1. ↑ Burke, John (1846). A Genealogical and Heraldic Dictionary of the Landed Gentry of Great Britain and Ireland. Henry Colburn. p. 672. https://books.google.com/books?id=2FE4AQAAMAAJ&pg=PA672.
2. ↑ Mahan, D.H. (1867). An Elementary Course of Military Engineering – Part I: Field Fortification, Military Mining and Siege Operations. John Wiley & Son. p. 76. https://books.google.com/books?id=7P1BAAAAYAAJ.
3. ↑ Battle of Alesia (Caesar's conquest of Gaul in 52 BC), Battlefield Detectives program, (2006), rebroadcast: 2008-09-08 on History Channel International (13:00-14:00 hrs EDST); Note: No mention of name caltrop at all, but illustrated and given as battle key to defend Roman lines of circumvallation per recent digs evidence.
4. ↑ Rawlinson, George. The Seven Great Monarchies Of The Ancient Eastern World, Vol 6. (of 7): Parthia. http://www.gutenberg.org/files/16166/16166-h/16166-h.htm#2HCH0023.
5. ↑ 5.0 5.1 Robert W. Reid (2006-09-01). "The Caltrop: A weapon that's barely changed over 2,300 years". https://www.historynet.com/weaponry-the-caltrop/#What Is A Caltrop?. "Today, it has reclaimed its old Greek name and reappeared as the tetrahedron, the bane of all vehicles running on pneumatic tires, and is used by both the military and police."
6. ↑ "Definition of Caltrop". http://www.merriam-webster.com/dictionary/caltrop.
7. ↑ "Definition of Caltrop". https://www.dictionary.com/browse/caltrop.
8. ↑ "Tribulus terrestris (puncture vine)". CABI. 8 November 2018. https://www.cabi.org/isc/datasheet/54447.
9. ↑ Charlton T. Lewis, Charles Short, A Latin Dictionary
10. ↑ Palm, Natalie; Franzaring, Jürgen; Schweiger, Andreas H. (2024). "International Biological Flora: Trapa natans †: No. 5". Journal of Ecology 112 (10): 2386–2420. doi:10.1111/1365-2745.14372.
11. ↑ Lewis, Charlton T.; Short, Charles (1879). "trĭbŭlus". A Latin Dictionary.
12. ↑ Lewis, Charlton T.; Short, Charles (1879). "mūrex". A Latin Dictionary.
13. ↑ τρίβολος. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project
14. ↑ Renatus, Flavius Vegetius (390). "Armed Chariots and Elephants". The Military Institutions of the Romans Book III: Dispositions for Action. http://www.pvv.ntnu.no/~madsb/home/war/vegetius/dere07.php#21. Retrieved 2005-10-22.
15. ↑ American Heritage. , March 1963.
16. ↑ Turnbull, Stephen (22 April 2008). Japanese Castles AD 250–1540. Bloomsbury USA. ISBN 9781846032530. https://books.google.com/books?id=U02pzwXNxBIC&pg=PA32. Retrieved 2 April 2018.
17. ↑ Samurai, Warfare and the State in Early Medieval Japan, Karl Friday, Psychology Press, 2004 P. 119.
18. ↑ Andreas Franzkowiak (2025). "issin sol behebet dir din füß gesunt – Eisensohlen gegen Fußangeln" (in de). Experimentelle Archaeologie in Europa Jahrbuch 2025 (Unteruhldingen: European Association for the advancement of archaeology by experiment) (24): 61–73. ISBN 978-3-944255-24-8.
19. ↑ Lovell 1964, pp. 42–43.
20. ↑ 20.0 20.1 Civil Defence Training Pamphlet No 2, p. 25.
21. ↑ "German Metal Spikes (Crowsfoot)". Tactical and Technical Trends. 5 November 1942. http://www.lonesentry.com/articles/ttt08/german-spikes.html.
22. ↑ Brooks, Walker (18 April 1944). "Caltrop". US2346713. European Patent Office. http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US2346713&F=0&QPN=US2346713.
23. ↑ Becker, Jonathan (13 July 1999). "Caltrop". US5921703. European Patent Office. http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US5921703&F=0.
24. ↑ "Spiky 'jack rocks' newest weapon in CAT strike". The New York Times. Associated Press. http://www.nwitimes.com/uncategorized/spiky-jack-rocks-newest-weapon-in-cat-strike/article_497e117d-f0ae-5829-8ac8-0846bb8e136e.html.
25. ↑ "CRIMINAL OFFENSES 720 ILCS 5 §21-1.4. Jackrocks violation.". ilga.gov. Illinois General Assembly. 1 January 2013. https://www.ilga.gov/legislation/ILCS/details?MajorTopic=RIGHTS AND REMEDIES&Chapter=CRIMINAL OFFENSES&ActName=Criminal Code of 2012.&ActID=1876&ChapterID=53&ChapAct=720+ILCS+5/&SeqStart=64900000&SeqEnd=67200000. Retrieved 9 January 2026. "a) A person commits a jackrocks violation when he or she knowingly: (1) sells, gives away, manufactures, purchases, or possesses a jackrock; or (2) places, tosses, or throws a jackrock on public or private property. (b) As used in this Section, "jackrock" means a caltrop or other object manufactured with one or more rounded or sharpened points, which when placed or thrown present at least one point at such an angle that it is peculiar to and designed for use in puncturing or damaging vehicle tires. ~. (d) Sentence. A jackrocks violation is a Class A misdemeanor."
26. ↑ Hambling, David. "Ukraine Drops Ancient Roman Weapons From Drones To Stop Russian Trucks" (in en). https://www.forbes.com/sites/davidhambling/2024/04/12/ukraine-teams-ancient-and-modern-weapons-to-stop-russian-trucks/.
27. ↑ "A to Z Guide to Heraldic Terms". Burkes Peerage and Gentry. http://www.burkes-peerage.net/articles/heraldry_c.aspx.
28. ↑ "The 'Caltrop' as Anti-Tank Obstacle". British Archaeology. http://www.britarch.ac.uk/projects/dob/crom1b.html.
29. ↑ "D-Day Beach Obstacles". 14 December 2019. https://www.d-daytoursnormandy.com/beach-obstacles-of-the-d-day-normandy-invasion/.

## References

* Clan Drummond, a brief history, at Scot Clans
* John L. Cotter and J. Paul Hudson, New Discoveries at Jamestown, Site of the First Successful English Settlement in America, 1957 Project Gutenberg
* Lovell, Stanley P (1964). Of spies & stratagems. Pocket Books. https://archive.org/details/ofspiesstratagem00love.

Official documents

* Ministry of Home Security (1944). Civil Defence Training Pamphlet No 2: Objects Dropped From the Air. His Majesty's Stationery Office.

* v
* t
* e

Fortifications

Ancient|

* Abatis
* Agger
* Broch
* Burgus
* Castellum
* Castra
* Castros
* Circular rampart
* City gate
* Crannog
* Ditch
* Defensive wall
* Dun
* Faussebraye
* Gatehouse
* Gord
* Hillfort
* Limes
* Oppidum
* Palisade
* Pincer gate
* Promontory fort
* Rampart
* Ringfort (Rath)
* Refuge castle
* Schwedenschanze
* Stockade
* Sudis
* Trou de loup
* Vallum
* Wagon fort (Laager)
* Vitrified fort

Post-classical|

* Advanced work
* Albarrana tower
* Alcazaba
* Alcázar
* Arrowslit
* Barbican
* Bartizan
* Bastion
* Battery tower
* Battlement
* Bent entrance
* Bergfried
* Bretèche
* Bridge castle
* Bridge tower
* Butter-churn tower
* Caer
* Caltrop
* Castle
* Chamber gate
* Chartaque
* Chashi
* Chemin de ronde
* Chemise
* Cheval de frise
* Citadel
* Coercion castle
* Concentric castle
* Corner tower
* Counter-castle
* Curtain
* Drawbridge
* Enceinte
* Embrasure
* Flanking tower
* Fortified buildings (church, house)
* Fujian tulou
* Ganerbenburg
* Gate tower
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* Toll castle
* Tower castle
* Tower house
* Turret
* Wall tower
* Bailey (or ward)
* Watchtower
* Witch tower
* Yett
* Z-plan castle
* Zwinger

Modern|

| 18th century
and earlier|

* Abwurfdach
* Bastion
* Blockhouse
* Breastwork
* Canal
* Caponier
* Casemate
* Cavalier
* Counterguard
* Counterscarp
* Couvreface
* Coupure
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* Device Forts
* Entrenchment
* Flèche
* Gorge
* Hornwork
* Kotta mara
* Lunette
* Orillon
* Ostrog
* Place-of-arms
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* Presidio (Spanish America)
* Punji sticks
* Ravelin
* Redan
* Redoubt
* Retrenchment
* Sandbag
* Scarp
* Sconce
* Schanze
* Sea fort
* Station
* Star fort
* Tenaille

|

19th century|

* Barbed wire
* Barbette
* Border outpost
* Bunker
* Coastal artillery
* Disappearing gun
* Fire control tower
* Gun turret
* Land mine
* Martello tower
* Outpost
* Polygonal fort
* Trench warfare
* Sangar
* Wire obstacles

20th century|

* Admiralty scaffolding
* Air raid shelter
* Anti-tank trench
* Barbed tape
* Belgian gate
* Blast shelter
* Blast wall
* Border security
* Buoy
* Bremer wall
* Concertina wire
* Defensive fighting position
* British "hedgehog" road block
* Czech hedgehog
* Dragon's teeth
* Entry control point (ECP)
* Electric fence
* Fallout shelter
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* Hardened aircraft shelter
* Hesco bastion
* Main line of resistance
* Pillbox
* Revetment
* Sentry gun
* Spider hole
* Submarine pen
* Tunnel warfare
* Underground hangar

By topography|

* Cave castle
* Hill castle
* Hillfort
* Hillside castle
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* Island castle
* Lowland castle
* Marsh castle
* Moated castle
* Promontory fort
* Ridge castle
* Rocca
* Rock castle
* Spur castle
* Water castle
* Floating water castle

By role|

* Coercion castle
* Counter-castle
* Ganerbenburg
* Hunting lodge
* Imperial castle
* Kaiserpfalz
* Landesburg
* Lustschloss
* Ordensburg
* Refuge castle
* Toll castle
* Urban castle

By design|

* Bridge castle
* Circular rampart
* Concentric castle
* L-plan castle
* Motte-and-bailey castle
* Quadrangular castle
* Ringfort
* Ringwork
* Tower castle

* See also:  Category

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