Caltrops were typically placed on roadways to slow attacking troops traveling by vehicle or animal.
The caltrop was “the simplest weapon we ever made” according to Dr. Stanley Lovell, author of Of Spies and Stratagems. No matter how the caltrop is tossed, it will land with one of its four prongs up. Whatever rolls over it will be punctured or injured. It is effective when many are scattered onto enemy roadways or airport runways.
Historically, caltrops have been found in Babylonian tombs, were used against medieval knights on horseback, and were found in archaeological digs at Jamestown.
For a bunch of cool spy stuff that might not be relevant here and the source: https://www.cia.gov/legacy/museum/artifact/caltrop-tire-spike/
Mythbusters tested them if you’re curious. In the James Bond car chase episode.
The vehicle they deployed then against was able to keep chasing them for a long while after running over them.
But specially made ones were way more effective iirc
Did myth busters make them so that hollow prongs broke off inside the tires? Because that’s how anti-vehicle caltrops are made these days.