Trou de Loup

A trou de loup, French for wolf hole, is a defensive obstacle consisting of a conical pit roughly 2 meters deep and 1.2 to 2 meters wide at the mouth, with a sharpened wooden stake driven into the bottom; the pits could be dug singly and hidden, or packed densely as an anti-personnel barrier, and were made more dangerous still when shallow-flooded, which hid them and added the risk of drowning. Although its French name is medieval, the device is far older: Julius Caesar described it in his Commentarii de Bello Gallico during the siege of Alesia, noting that his own soldiers called the pits lilies for their resemblance to the flower, and Roman examples of the same obstacle survive at Rough Castle on the Antonine Wall in Britain. Armies continued to dig pit obstacles of this kind for centuries after, into the medieval period and beyond.