Q. A. Gillmore to 214 COASTS OF 8. C., GA., AND MIDDLE AND EAST FLA. [Cuar. XV, December 25, 1861

Hilton Head, S. C., December 25, 1861.

Brig. Gen. THOMAS W. SHERMAN, Commanding Expeditionary Corps, Hilton Head, S. O.:

SIR: In response to your verbal directions to me I have the honor to submit a plan, or rather the prominent featt res of a plan, for obtaining possession of the city of Charleston, S. C.

Three projects for attaining this object naturally suggest themselves for our examination, viz:

Ist. By way of Morris and Sullivan’s Islands, involving the reduction of Forts Sumter and Moultrie, Johnson, and Castle Pinckney, and the subsequent bombardment of the city. The fall of Forts Sumter and Moultrie would insure the success of this project if the Navy could co operate with us afterwards.

2d. By way of Stono Inlet and River and James Island, taking Fort Johnson, and leaving Forts Sumter, Moultrie, and Castle Pinckney on the right for the time being. We could not occupy Fort Johnson, however, until Sumter had been reduced.

3d. By way of Bull’s Bay, leaving all the forts in the harbor on the left, and taking the city in the rear by Wando and Cooper Rivers.

The Bull’s Bay project presents the greatest difficulties in the way of land and water transportation; would probably for other reasons be the most difficult of execution, and I therefore would not recommend a principal attack in that direction. A feint there in force would in my opinion very materially second the initial steps of any offensive operations on James Island via Stono River.

As between the other two projects I distinctly favor that by James Island for the following prominent reasons, without going into details, viz:

First. The recent blockade of the channels leading into Charleston Harbor by old hulks. Although it will most likely eventuate in opening one good channel for vessels of moderate draught, it will, for some time to come at least, practically exclude any effective co-operation of the Navy in a direct attack from the sea;

Second. The complete success of the first project (by first reducing the forts) would neither give us the possession of Charleston as the objective point nor a good base of operations, unless we had all of James Island also; while,

Third. If we have James Island we command and can even hold the city, and of course secure all the real advantages which its possession is supposed to confer, even if the forts in the harbor (that is, Sumter and Moultrie) remain in the hands of the enemy.

Fourth. The attack by James Island would render it necessary for the Navy first to shell out the battery or batteries on Stono Inlet and River, so as to secure to us the undisputed command of those waters up to the first good landing place on the island, probably Turnbull. Having a footing on the island, we would have to fight a battle for its possession. If beaten, a position on the south of the island could be maintained against very great odds, even in the absence of any active assistance from the Navy.

It would be equally necessary to fight and gain this battle on James Island in order to hold and oceupy Charleston, even if we first captured the harbor per se by reducing the forts by a siege. Once in possession of James Island and holding the sea, the forts fall into our hands in due time as a matter of course. The reduction of Fort Sumter, or even Fort Moultrie, with an investment by water only, is a matter of no small moment.

As an isolated movement, not really seconded by descent on other important points of this coast, I would consider the followiug force sufficient to carry this project by James Island into effect. Our knowledge, of the extent of the preparations against such an attempt by us is quite meager, and radical modifications of this plan may be necessary so far asit relates to the proportion of the different arms when a thorough reconnaissance shall have placed us in possession of more facts. I should consider the following as simply a near approximation to what is required, viz: 14,000 infantry, 1,000 cavalry, 12 pieces light artillery (two light batteries), 20 siege guns, with a large proportion of 20-pounder and 30-pounder Parrott guns.

Very respectfully, your obedient servant,

Captain, and Chief Engineer Expeditionary Corps,

Port ROYAL, S. C., December 27, 1861.

Gereral GEORGE B. MOCLELLAN,

Commanding U. 8. Army:

DEAR GENERAL: The Ocean Queen arrived yesterday with a mail,

but brought no news of any cavalry. Had I cavalry and another light