Caltrops were first used as early as 331 BC at the Battle of Gaugamela. This was the decisive battle between Alexander the Great and his Macedonian army, and King Darius III of the Persians.

Where did the caltrop come from?

Caltrop (Tribulus terrestris) is a summer-growing weed found widely throughout Western Australia. It is most common in areas of frequent spring and after summer rain.

Why are caltrops illegal?

According to the Smith County Sheriff's Office, the caltrops are made from rebar. They are sharpened to four metal points so that there is always a sharp edge sticking up. ... Even possessing caltrops is a felony in Texas. It's also illegal to manufacture, transport, repair, or sell them.