CONFIDENTIAL.] HDQRS. MIL. DIV. OF THE MISSISSIPPI,

Nashville, Tenn., April 24, 1864.

Major General J. B. McPHERSON,

Commanding Department of the Tennessee, Huntsville:

GENERAL: I telegraphed you last night that Colonel Comstock had come from General Grant with a letter; that he (General Grant) would be ready by the 27th to take the initiative, if in the mean time Lee did not, and of course he wants me to act at the same time, but Colonel Comstock tells me he does not think General Grant can do anything till May 2.

Of course the movement in Virginia is the principal and ours is secondary and must conform. We must be as far ready as possible.

First. Give General Slocum and Washburn orders to seem most active; to hold there all the enemy possible, even at a small risk to the river, for if we whip Joe Johnston good, everything lying west will feel the blow.

Second. Do all that is within the power of mortal to get up your two divisions from Cairo, with wagons, beef-cattle, &c. I will write to Lieutenant-Commander Shirk, U. S. Navy, to watch the Tennessee all that is possible to prevent any damage to our roads from that quarter.

Third. You should at once move your effective force of the Fifteenth Corps to the neighborhood of Larkin's, or wherever you propose to cross, ready to move on Lebanon. Dodge's command should cross at Decatur and brush away that cavalry, and move on Guntersville and Lebanon. From Lebanon your army should move, as light as possible, by Summerville or other good route toward La Fayette or Villanow to communicate with Thomas. From La Fayette you can renew your supply of bread, salt, sugar, and coffee from Ringgold, to which point we have cars. We are accumulating stores as fast as possible at Chattanooga. If you can start with twenty days' supply it is all that I now expect. I will explain to Comstock and send word to General Grant how important it is we should have the two divisions now at Cairo and on furlough, and have him correspond by telegraph with them at Cairo, and judge when they can reach your right flank via Clifton.

You should have a force of about 30,000, exclusive of Garrard's cavalry, which will remain with your extreme right till we are beyond the Coosa, when it must strike for the Montgomery and Atlanta road.

I think I understand the cavalry force in front of Dodge. It is a detachment from Johnston sent there to watch your operations, but the moment you cross the Tennessee in force it will hasten to cover Rome, and watch Johnston's left flank and rear.

The worst we have to apprehend is that Forrest may come across to act against our right flank, but this would be prevented if Washburn and Slocum threaten Grenada.

I take it for granted that unless Banks gets out of Red River and attacks Mobile, which is a material part of General Grant's plan, that we will have to fight Polk's army as well as Johnston's. General Corse has returned. Banks would not spare Smith. Indeed, it appears that Smith's force is the real substance of his army. He was shipped near Mansfield and retreated to Grand Ecore, 40 miles, though Banks claims a victory; but from what General Corse tells me, he might have made it a victory by going ahead, but by retreat-