After the Battle of Port Royal, the Union planned an expedition against Charleston, capturing Edisto and John's Island, and by June 2, they had 20 vessels in the Stono Inlet.

Gen. Henry Benham, to James Island, where they entrenched at Grimball's Landing near the southern flank of the Confederate defenses.

[3]: 154, 157, 171 At about 4:30 a.m. on June 16, the Northern troops attacked the Confederate fort at Secessionville where Colonel Thomas G. Lamar commanded about 500 men who had a number of very heavy artillery guns and a good field of fire.

The 8th Michigan were "mowed down in swaths" from "a shower of musket balls and discharges of grape and canister" from the Confederate cannon, according to one Union officer.

Lt. Col. Joseph Hawley's 7th Connecticut's advance halted when their left flank became mired in the marsh mud and their right received canister and grape.

Alfred P. Rockwell, finally started firing on the Confederate garrison as the Highlanders of the 79th New York under Lt. Col. David Morrison advanced.

The 100th Pennsylvania Roundheads, under the command of Maj. David Leckey, tried to support the Highlanders, but their attack stalled as did the previous ones with Confederate canister and grape.

Col. Rudolph Rosa's 46th New York tried to line up on the 100th's left, but some retreated with the fleeing Irish 28th Massachusetts and the 7th Connecticut, while the remainder received Confederate canister.

On the other side of the marsh to the north was a piece of land the 3rd New Hampshire under Lt. Col. John H. Jackson, supported by Maj. Edwin Metcalf's 3rd Rhode Island Heavy Artillery, used to advance upon the right flank of Tower Battery.

However, 150 yards of marsh prevented any Union advance upon the fort's defenders, while Confederate batteries to the north fired into their backs.

"[3]: 224, 252 Hunter relieved Benham of his command for disobedience, citing the 10 June directive forbidding an attack on Charleston or Fort Johnson, and placed under arrest.

[3]: 280–281, 288, 291 On 26 Jan. 1863, Judge Advocate General of the United States Army Gen. Joseph Holt decided Benham's attack was justified and was not prohibited by the 10 June directive.