How did medieval engineers use mining to bring down castle walls?

In the context of medieval military engineering, mining was a highly effective method used to breach stone fortifications.12

To execute this, engineers would dig a gallery—a tunnel—directly beneath the foundation of a castle wall. As the tunnel progressed, they used wooden shoring to support the weight of the earth and the heavy masonry above. Once the gallery was sufficiently excavated under the target section of the wall, the engineers would fill the space with combustible materials and set them on fire. As the wooden supports burned away, the gallery would collapse, removing the structural foundation and causing the wall above to crumble.12

This tactic required specific ground conditions and was always at risk of being countered by defenders, who might attempt to dig their own tunnels to intercept and destroy the attackers' mine. To defend against such threats, medieval architects designed towers with massive, protruding feet to make undermining more difficult.13