I sent a response to Gen. McClernand’s letter.
HEADQUARTERS DEPARTMENT OF THE TENNESSEE, Before Vicksburg, January 31, 1863.
Major General John A. McClernand,
Commanding Thirteenth Army Corps:
GENERAL: The intention of General Orders, Number 13., is that I will take direct command of the Mississippi River expedition, which necessarily limits your command to the Thirteenth Army Corps.
In charging the Thirteenth Army Corps with garrisoning the WEST bank of the river, I add to it any forces belonging to any command on that bank not already assigned to other corps, and, instead of weakening your force in the field, it will strengthen it by about 7,000 men, still leaving a proper garrison at Helena, the only place I now deem necessary to garrison. All forces and posts garrisoned by the Thirteenth Army Corps are under your command, subject, of course, to directions from these headquarters.
I regard the President as Commander-in-Chief of the Army, and will obey every order of his, but as yet I have seen no order to prevent my taking immediate command in the field, and since the dispatch referred to in your note, I have received another from the General-in-Chief of the Army, authorizing me directly to take command of this army.
I at first thought I would publish no order taking command, but soon saw it would be much more convenient to issue orders direct to corps commanders whilst present with the command than through another commander.
Your obedient servant,
U. S. GRANT,
The Papers of Ulysses S Grant, Vol 7, p 264
O.R., I, xxiv, part 1, p 13