During the siege of the Star Fort, after the Patriots came within striking distance of the fort walls, Kosciuszko adopted the classic siege tactic of a mine. The plan was to pack gunpowder into the mine's primary tunnel and detonate it to create a breach so Greene's men could rush into the fort from nearby approach trenches. Laborers began digging the main shaft with picks and shovels on June 9, 1781, but progress through the hard earth in late spring heat and under constant Loyalist fire was painfully slow. On June 11, 1781, General Nathanael Greene urged General Andrew Pickens to send the needed powder at once. Before the mine could be completed or used, the siege ended when Greene, learning that Loyalist reinforcements were coming, called off the effort, and digging stopped short of the fort's ditch. The cone-shaped earthen passage, built without beams or supports, ran 125 feet from end to end and survives as a unique example of Revolutionary War-era mine construction and as one of the few remaining earthworks of the Revolutionary War.