From the Medieval Ages to today, still effective. Found Caltrops

EUC, DK Eyewitness Books Knight, hardcover 9780756606954

Journal — Ian Ross

A History of Weapons: Crossbows, Caltrops, Catapults & Lots of Other Things that Can Seriously Mess You Up eBook : O'Bryan, John, Orkin, Barry: Kindle Store

Caltrop - Wikipedia

Spiked Defenses: The Tactical Use of Caltrops in Medieval Warfare

3rd-4th century A.D. or later. Composed of four arms tipped with triangular spikes. Cf. Beutler, F. et al., Der Adler Roms. Carnuntum und die Armee

Roman Iron Anti-Cavalry Caltrop

During the Medieval period, how did infantrymen deal with cavalry? - Quora

Collection of Caltrops From Medieval Times Through World War II sold at auction on 4th May

The Weirdest Medieval Weapons: A Journey into Historical Oddities

Caltrop Weapons

Fuck The Noise, Get Off The Internet: An Interview With Joseph Rathgeber – gingerslim

Medieval technology - Wikipedia