The summer months of 1864 marked a full year for Rear-Admiral John Dahlgren in command of the South Atlantic Blockading Squadron. Originally his assignment was to command the monitors operating against Charleston, with the objective to redeem some of the Navy’s prestige lost with the failed ironclad attack on Fort Sumter (in April 1863). With the death of Rear-Admiral Andrew H. Foote, before either man arrived in the department, Dahlgren instead took command of the squadron. But Dahlgren’s objective remained – Fort Sumter thence Charleston.
Through the long summer campaign that followed and the fall bombardments, Dahlgren’s objective stared back defiantly. Through the winter months, around the interruption due to his son’s death, Dahlgren offered several plans to gain Charleston, to no avail. To gain Charleston either Dahlgren had to risk the monitors or support an Army offensive to bypass the Confederate harbor defenses. He avoided the former, but continued to propose the later. And in the Army’s view, the route to Charleston promised to be a risky and prolonged campaign. So every time Dahlgren proposed an advance across James Island, the Army’s response relied on the Army’s information on the subject. Dahlgren could not offer a rebuttal. That changed in July 1864, as Dahlgren went ashore on James Island during Major-General John Foster’s operations there. And he came back with what he felt was proof his plan would work. In a report to the Secretary of Navy, Guideon Wells, he put down details of this plan on August 1, 1864. This report was, in part, a summary of operations in July to include naval support of Foster’s operations. But most of the text focused on this plan to turn the Confederates out of Charleston.
On further consideration, I believe that with 10,000 good soldiers added to the present force we could turn the rebel defense on James Island and reach Charleston, and I observe from the rebel papers that the idea was apprehended by them.
If, during the lull before Richmond, General Grant could spare the men for three weeks, I feel sure that the rebels could be so disturbed here as to assist him and General Sherman by dragging off force from Richmond.
This sketch will explain: “P-S” is the rebel line of works extending from the Stono River to the marsh separating James Island from Folly Island. Battery Pringle (“P”) is a regular earthwork of 8 guns, with bombproofs and full traverses. A little farther is battery Tynes, with 5 guns, both carefully built. Secessionville is on the left; its strength was tried by General Benham in 1862; there are intermediate works. “A” is our advanced position from Folly Island. The ground between is controlled and picketed by the rebels, but not held in force, and they (on it) fall back to the lines when pushed vigorously. “B” was the position of our left under General Hatch.
The fleet held the river and connected our right and left; it was in fact the center of operation; the channel is very narrow and has just water to pass a monitor.
“C” is the extreme of a narrow belt of woods extending from Mr. Paul Grimball’s house below the bend. Here I offered to plant a battery of ten 100-pounders or XI-inch guns, which could be done unperceived under cover of the woods, and silence Pringle and Tynes (distant 1,700 yards); this done two monitors would move up and enfilade the line.
It was indispensable, however, that the position at “B” should be held securely, or the naval battery at “C” would be lost; the monitors once above Pringle would sweep the ground in front of “B.”
Ten thousand men could be moved without baggage in three days by water from Fortress Monroe, and the blow struck quick as lightning.
Pringle and Tynes once treated as designed, the troops could cross from “B” to their rear and render the rebel lines useless.
I have seen nothing that promises so well with so small a force, and the rebels are unprepared for such an exigency; they certainly were so when we held the ground as indicated. As it was, General Hatch did actually reach “B,” but as he moved obliquely across John’s Island from the Edisto, the rebels used the time to collect and were in force, so that after two or three conflicts it was deemed best to retire, which was done to an engineer’s wharf in the rear of the fleet; the men were embarked without a shot fired at them. I held position until the next day. General Schimmelfennig had advanced from “A” and drove the rebels vigorously before him, seizing two cannon; the ground between his front and the rebel line being swept continually by the guns of the fleet, he was not disturbed.
The land movements proposed were largely repeats of previous operations on John’s Island. The geography of that island made direct movements exposed to Confederate flank attacks, while constraining Federal movements to narrow corridors.
The plan is well worth considering, and if undertaken by a column of good troops, will, I feel sure, endanger Charleston and produce corresponding effect. General Foster does not consider it feasible with the small force he has. I feel sure of my part.
By the time this report reached Washington, D.C. the Army was in the process of reducing the troops in the department, not increasing. The presence of Confederates in the lower Shenandoah was at that moment in time the pressing concern. As Chambersburg burned, Lieutenant-General U.S. Grant was less interested in opportunities – fleeting opportunities – outside Charleston. Grant had already weighed in on the issue months before. Foster was to demonstrate and remain active, but not take up major offensive operations.
And for what it was worth, Foster did not share Dahlgren’s optimism for operations on John’s Island. Very unlikely for the Confederate batteries to fall after a short siege. Nor for the Confederates to simply give up the approaches to Charleston. There were, of course, a couple more belts of defenses between the lines mentioned by Dahlgren and the city. If the plan were to go forward, Foster would need to feel sure of his part. Clearly Foster had a better grasp of the situation.
(Citation from ORN, Series I, Volume 15, pages 591-2.)