Gilmore ordered his siege guns and mortars to begin a bombardment of the fort on July 18 and they were joined by the naval gunfire from six monitors that pulled to within 300 yards of the fort. The bombardment lasted eight hours, but caused little damage against the sandy walls of the fort, and in all, killed only about 8 men and wounded an additional 20, as the defenders had taken cover in the bombproof shelter.[3]