Castle Learning Center Undermining
Castles of Britain

Undermining

mining drawing © 1998-2016 by Lise Hull
Undermining of a castle wall or tower was one of the most feared events by the Lord of the castle, for it led to his defeat.

Undermining was carried out by "sappers" or miners. They would dig a subterranean passage under the walls or tower of the castle for the purpose of gaining access or to collapse the structure.

Mining was in response to the stone keeps, towers, and walls that could not be burned or battered down with primitive siege engines. While digging the tunnel, the sappers would build wooden supports. After completing the tunnel, brush mixed with hog fat, would be placed near the wooden supports. Sometimes whole hogs would be placed in the tunnel.

After the placement of the flammable material all the sappers would be ordered to leave the tunnel, with the exception of the torchman. He would set the tunnel on fire and run for the tunnel opening.

As the wooden tunnel supports burned they would collapse, in turn the stone walls, or towers would also collapse. At times, the tunnel would collapse pre-maturely and trap all who were doing the tunnel work. Mining was a very risky type of employment, and not for the faint of heart.

Mining was undertaken at Rochester Castle in 1215, at Dover Castle in 1216, and at Dryslwyn castle in 1287.