Sapping

Common card · No. 471677

Sapping is a term used in siege operations to describe the digging of a covered trench (a "sap") to approach a besieged place without danger from the enemy's fire. The purpose of the sap is usually to advance a besieging army's position towards an attacked fortification. It is excavated by specialised military units, whose members are often called sappers. By using the sap, the besiegers could move closer to the walls of a fortress, without exposing the sappers to direct fire from the defending force. To protect the sappers, trenches were usually dug at an angle in zig-zag pattern (to protect against enfilading fire from the defenders), and at the head of the sap a defensive shield made of gabions (or a mantlet) could be deployed. Once the saps were close enough, siege engines or cannon could be moved through the trenches to get closer to—and enable firing at—the fortification. The goal of firing is to batter a breach in the curtain walls, to allow attacking infantry to get past the walls...

Read on Wikipedia · Image Haas & Peale, photographer., Public domain