The center had been in Virginia and the Trans-Mississippi West for a long time, but in the summer of 1863 there was a strong movement from the Union to capture Charleston, South Carolina. That was where the first ordinance of secession had been approved, and Charleston had long been the place of the most virulent anti-federal sentiment. To capture Charleston, and avenge the loss of Fort Sumter, was therefore a major desire on the part of the Union leaders.

In the spring and early summer of 1863, the Union Navy commenced furious bombardments against the numerous forts that protected the harbor at Charleston. By mid-July, the guns of the fleet had softened up the defenses to the point at which the Army leaders were willing to risk a land assault on the forts on the southeast side of the harbor.