They Used Tunneling to Surprise Their Enemies
During the time of the Roman Legion siege warfare happened often and there were few armies better at it than the Romans. One of their most successful strategies, for a time, was tunneling. Instead of just waiting out the siege and hoping the city or building eventually surrendered, they would just tunnel underground. By tunneling they could easily get under the defensive walls that were keeping them out. For awhile this was a very effective tactic and led to a number of successes for the Romans. But eventually Rome’s enemies learned of this strategy and began defending against it.
One such defense by the people of the city of Themiscyra in the early first century BC was to find the tunnel and drive wild animals into it. They filled the tunnel with bears and bees which made quick work of the Romans who were stuck together in cramped quarters. Rome’s enemies even began using tunnels themselves and in the 3rd century AD it was the Romans who had to defend against tunneling Sassanian Persians. The Romans built their own tunnels to get to the attackers and stop them. Evidence has been found of this massive underground battle and the amount of fighting done in the tunnels is astonishing.
But the underground aspect of the battle is not the most intriguing part. This battle was the first known use of chemical warfare. The Persians burned bitumen and sulfur crystals in order to create a gas cloud which suffocated the Romans.