HEADQUARTERS WESTERN DEPARTMENT,
Murfreesborough, Tenn., February 25, 1862.

SIR: The fall of Fort Donelson compelled me to withdraw the remaining forces under my command from the north bank of the Cumberland and to abandon the defense of Nashville, which but for that disaster it was my intention to protect to the utmost. Not more than 11,000 effective men were left under my command to oppose a column of General Buell's of not less than 40,000 troops, moving by Bowling Green, while another superior force, under General Thomas, outflanked me to the east, and the army from Fort Donelson, with the gunboats and transports, had it in their power to ascend the Cumberland, now swollen by recent flood, so as to intercept all communication with the South. The situation left me no alternative but to evacuate Nashville or sacrifice the army. By remaining the place would have been unnecessarily subjected to destruction, as it is very indefensible, and no adequate force would have been left to keep the enemy in check in Tennessee.

Under these circumstances I moved the main body of my command to this place on the 17th and 18th instant, and left a brigade under General Floyd to bring on such stores and property as were at Nashville, with instructions to remain until the approach of the enemy, and then to rejoin me. This has been in a great measure effected; and nearly all the stores would have been saved but for the heavy and unusual rains, which have washed away the bridges, swept away portions of the railroad, and rendered transportation almost impossible. General Floyd has arrived here.

The rear guard left Nashville on the night of the 23d. Edgefield, on the north bank of the Cumberland, opposite the city, was occupied yesterday by the advanced pickets of the enemy.

I have remained here for the purpose of augmenting my forces and securing the transportation of the public stores. By the junction of the command of General Crittenden and the fugitives from Fort Donelson, which have been reorganized as far as practicable, the force now under my command will amount to about 17,000 men. General Floyd, with a force of some 2,500 men, has been ordered to Chattanooga, to defend the approaches towards Northern Alabama and Georgia and the communication between the Mississippi and Atlantic and with the view to increase his forces by such troops as may be sent forward from the neighboring States.

The quartermaster's, commissary, and ordnance stores which are not required for immediate use have been ordered to Chattanooga, and those which will be necessary on the march have been forwarded to Huntsville and Decatur. I have ordered a depot to be established at Atlanta for the manufacture of supplies for the Quartermaster's Department and also a laboratory for the manufacture of percussion caps and ordnance stores, and at Chattanooga depots for distribution of these supplies. The machinery will be immediately sent forward.

Considering the peculiar topography of this State and the great power which the enemy's means of transportation affords them upon the Tennessee and Cumberland, it will be seen that the force under my command cannot successfully cover the whole line against the advance of the enemy. I am compelled to elect whether he shall be permitted to occupy Middle Tennessee, or turn Columbus, take Memphis, and open the valley of the Mississippi. To me the defense of the valley appears of paramount importance, and, consequently, I will move this corps of the army, of which I have assumed the immediate command, towards the left bank of the Tennessee, crossing the river near Decatur, in order to enable me to co-operate or unite with General Beauregard for the defense of Memphis and the Mississippi.

The Department has sent eight regiments to Knoxville for the defense of East Tennessee, and the protection of that region will be confided to them and such additional forces as may be hereafter sent from the adjacent States. General Buckner was ordered by the Department to take command of the troops at Knoxville; but as he was at that time in presence of the enemy, the order was not fulfilled. As it would be almost impossible for me under present circumstances to superintend the operations at Knoxville and Chattanooga, I would respectfully suggest that the local commanders at those points should receive orders from the Department directly or be allowed to exercise their discretion.

I have the honor to remain, very respectfully, your obedient servant,

                    A. S. JOHNSTON,

 General, C. S. Army.

Hon. J.P. BENJAMIN,

Secretary of War, Richmond, Va.