In September 52 BC, Julius Caesar had a problem. He was deep inside Gaul (modern day France) besieging his last great Gaul enemy, Vercingetorix, at the latter’s fort of Alesia. With his force of around 60,000 infantry and cavalry, Caesar built a second wall around Vercingetorix’s fort in order to starve his foe into surrender.

For a time, it looked like Caesar was succeeding.