Foot traps or caltrops are simple defensive weapons with enormous tactical effectiveness against infantrymen and horses. Written sources date back to the 4th century BC, but their invention probably goes back much further. Both historical and modern footwear offers little protection against them. The sharp spikes easily pierce through soles and feet. In the best case scenario, the victim can pull a caltrop without barbs out of their foot, but with barbed tips this is no longer possible without additional injury. To protect the feet, authors of military manuscripts from the 15th to the early 17th century regularly recommend iron soles that are strapped under the shoes like wooden clogs. Beyond the pictorial and rare textual sources, no original iron soles are known so far, so it is unclear whether they actually existed or not.
Since 2014 we have been involved in cooperation with the City Museum Ingolstadt and the Bayerisches Landesamt für Denkmalpflege (Bavarian State Office for Monument Protection) in a project for the re-investigation and publication of the ceramic grenades, found in 1983 near the New Castle of Ingolstadt. Unfortunately, this find has not yet been scientifically edited and appropriately published, especially in view of it's importance for the military-historical and weapon-technological research.