 After being appointed as a brigadier general, Gillmore took charge of the siege operations against Fort Pulaski.A staunch advocate of the relatively new naval rifled guns, he was the first officer to effectively use them to knock out an enemy stone fortification.More than 5,000 artillery shells fell on Pulaski from a range of 1,700 yards during the short siege, which resulted in the fort's surrender after its walls were breached.