HEADQUARTERS, Columbus, MISS., March 31, 1863.

SIR: I have the honor to state for the information of the lieutenant-general commanding that the recent orders, Number 68, interposing a FIFTH District between the First District and the enemy's lines, has had a tendency to complicate the question of the defense of this important region of the State of Mississippi as well as a portion of Alabama.

Previously to the receipt of that order, I had sent Lieutenant-Colonel [C. R.] Barteau with his cavalry to Verona, which is in one of the two northern counties of the State, in the execution of an important service connected with the accumulation of subsistence; also with the defense of the district on a plan which I had in view whenever I should have force enough to put it in execution; and I only waited for Major [W. A.] Hewlett's Thirteenth Battalion Alabama Partisan Rangers to be sufficiently recovered from measles and other diseases to push them forward to Smithville or vicinity, provided I could re-enforce him by two or three more companies in a serviceable condition.

I have hitherto delayed the movement from these still existing causes and the impracticability of obtaining information of the movements of the enemy, within a district over which I have no control or jurisdiction, in time to make movements and combinations with my few troops placed on the immediate border of the district through which they would in all probability come.

The presumption is that if the enemy makes a heavy raid on Columbus, he will move upon the ridge along which the great military road runs from this point to Tuscumbia, and which route alone is practicable during periods of high water, such as have prevailed since my arrival in this district, and this obstruction alone in all probability has hitherto delayed movements of the enemy in this direction.

Knowing the pressing demands for troops and military supplies in other quarters, I deemed it proper to delay pressing the wants of this district on your attention until the last moment, and did not, therefore, make any formal application for troops and munitions until the 6th instant, when I laid the subject fully before you in a letter, and subsequently in memoranda furnished to Colonel [W. S.] Lovell and Major Bradford, [assistant] inspector-general, and gave them such information as to me seemed important.

The public mind has apparently followed me very closely on this [question of the protection of their homes and firesides.

It is to be observed that the establishment of an infantry force at Aberdeen would be within supporting distance of Cotton Gin, Okolona on the west, and Smithville on the east, but would not be sufficiently available against a cavalry raid, making a circuit in Alabama, on Columbus. Okolona is less likely to be attacked than Columbus and Aberdeen. Aberdeen ought to be defended so far as may be practicable, as well as Columbus.

The strategic position of Columbus, in the valley of the Tombigbee, the great grain region of the State, covering the railroad connection between the east and the west, and the important port of Mobile, renders its defense and retention a necessity, especially as, from its locality between two rivers, mainly impassable, and the extended double line of intrenchments, at great cost now completed, it would become a SECOND Corinth, and paralyze our military movements and withstand all efforts, even the most formidable, short of a regular siege, or grand escalade, for its recovery.