With Fort Sumter in Confederate hands, the port of Charleston became an irritating loophole in the Federal naval blockade of the Atlantic coast. In two months of 1863, 21 Confederate vessels cleared Charleston Harbor and 15 entered. Into Charleston came needed war supplies; out went cotton in payment. To close the port -- and also capture the city -- it was necesary first to seize Fort Sumter, now repaired and armed with some 95 guns. After an earlier Army attempt had failed on James Island, the job fell to the U.S Navy, and Rear Adm. Samuel F. Du Pont was ordered to take the fort.
On the afternoon of April 7, 1863, nine armored Monitor vessels steamed slowly into the harbor and headed for Fort Sumter. For 2 and /12 hours the ironclads dueled with Confederate batteries in the forts and around the harbor. The attack only scarred and battered Sumter's walls, but the far more intense and accurate Confederate fire disabled five Federal ships, one of which, the "Keokuk," sank the next morning.
When the ironclads failed, Federal strategy changed. Du Pont was removed from command and replaced by Rear Adm. John A. Dahlgren, who planned to combine land and sea operations to seize nerby Morris Island and from there to domolish Fort Sumter. At a position secured by U.S. forces on Morris Island, Union troops under Brig. Gen. Quincy A. Gillmore began to place rifled cannon powerful enough to breach Sumter's walls.
Meanwhile, Confederate laborers and slaves inside Fort Sumter worked day and night with bales of cotton and sand to buttress the walls facing the Federal guns. The fort's garrison at this time consisted of five companies of the First South Carolina Artillery under Col. Alfred Rhett.
Federal troops fired a few experimental rounds at the fort in late July and early August. The bombardment began in earnest on August 17, with almost 1,000 shells being fired the first day alone. Within a week, the fort's brick walls were shattered and reduced to ruins, but the garrison refused to surrender and continued to repair and strengthen the defenses.
Palmetto-log reinforcements on the channel side wall of the Fort
Confederate guns at Fort Moultrie and other points now took up the defense of Sumter. Another Federal assault on September 9 fell short; this time the attackers lost five boats and 124 men trying to take the fort from Maj. Stephen Elliott and fresh Confederate troops under his command. Except for one ten-day period of heavy firing, the bombardment continued intermittently until the end of December. By then, Sumter's cannon were severely damaged and dismounted and its defenders could respond with only "harmless musketry."
In the summer of 1864, after Maj. Gen. John G. Foster replaced Gillmore as commander of land operations, the Federals made one last attempt to take Sumter. Foster, a member of Anderson's 1861 garrison, believed that "with proper arrangements" the fort could be taken "at any time." A sustained two-month Union bombardment, however, failed to dislodge the 300-man Confederate garrison and Foster was ordered to send most of his remaining ammunition and several regiments of troops north to aid Grant's campaign against Richmond.
Desultory fire against the fort continued through January 1865. For 22 months Fort Sumter had withstood Federal seige and bombardment, and it no longer resembled a fort at all. But defensively it was stronger than ever. Big Federal guns had hurled seven million pounds of metals at it, yet the Confederate losses during this period had been only 52 killed and 267 wounded.
Gen. William T. Sherman's troops advancing north from Savannah, however, caused the Confederate troops to be withdrawn, and Fort Sumter was evacuated on February 17, 1865.