The failure of the Union offensive against Charleston in the spring of 1862 and the transfer of troops to Virginia diminished the size of Federal forces in the region. Union commanders settled for conducting raids against the Savannah-Charleston Railroad and small settlements throughout the low country as they waited for a new campaign. Meanwhile, the U.S. Navy tightened its blockade of the city and awaited a fleet of ironclad warships for use in operations against the forts protecting Charleston Harbor.
As Federals conducted their small operations, the Southern commander, General P.G.T. Beauregard, set about strengthening his defenses. Beauregard was a highly skilled engineer and when the Federal navy launched an ironclad attack against the harbor on April 7, it was driven back by heavy and accurate artillery fire from Forts Sumter, Moultrie, Johnson, and many smaller supporting batteries.
Following the naval defeat, the overall Federal commander, General Daniel Hunter, was replaced by the more industrious General Quincy A. Gillmore. The victor of Fort Pulaski in 1862, Gillmore conducted an aggressive campaign targeting Fort Wagner and Battery Gregg on the eastern tip of Morris Island. From these positions Union heavy artillery could bombard Fort Sumter and Charleston itself. Gilmore landed on Morris Island on July 11 and conducted active operations against Fort Wagner, settling into a siege after initial frontal assaults failed.
The Siege of Fort Wagner lasted until September 6 when Confederates evacuated Morris Island. Three days later Gillmore ordered an amphibious assault upon Fort Sumter but the attackers were driven back. Unable to secure Fort Sumter or make headway against the other defenses defending the city, Gillmore conducted an active bombardment of Charleston. No further major actions were taken against Charleston and the city held out until February 1865.