Sapping is a term used in siege operations to describe the digging of a covered trench to approach a besieged place without danger from the enemy's fire. The purpose of the sap is usually to advance a
Union troops of the 1st New York Engineers digging a sap with a sap roller on Morris Island, 1863
The star-shaped Fort Bourtange, restored to its 1750 condition, is an example of a trace italienne fort.