President's War Order No. 3 
Order, No. 3 } Washington, March 11, 1862.
Major General McClellan having personally taken the field at the head of the Army of the Potomac, until otherwise ordered, he is relieved from the command of the other Military departments, he retaining command of the Department of the Potomac.
Ordered further that the two departments now under the respective commands of Generals Halleck, and Hunter together with so much of that under General Buell as lies West of a North and South line indefinitely drawn through Knoxville, Tennessee, be consolidated, and designated the Department of the Mississippi; and that, until otherwise ordered, Major General Halleck have command of said department.
Ordered also, that the country West of the Department of the Potomac, and East of the Department of the Mississippi be a Military department to be called the Mountain Department; and that the same be commanded by Major General Fremont.
That all the commanders of departments, after the receipt of this order by them respectively, report severally and directly to the Secretary of War, and that prompt, full, and frequent reports will be expected of all and each of them. ABRAHAM LINCOLN
 ADS, IHi. A preliminary draft of this order prepared by Stanton is as follows:
``In view of active operations by the Army of the Potomac which will demand the presence & supervision of its Commanding General in the field and that he should be relieved from all other duties is ordered by the President
``1st. That Major General George B McClellan be and he is hereby relieved from & after this date from duty as General Commanding and directed to devote his attention exclusively to the operations of the Army of the Potomac
``2. The Adjutant General is directed to give immediate notice of this order to all Generals commanding Armies expeditions or Departments and instruct them from and after the receipt of this order to make their reports to & receive their instruction from the President through the War Department.'' (DLC-Stanton Papers).
The issuing of War Order No. 3 was also recommended by Bates in the cabinet meeting of March 11 (see Diary of Edward Bates, p. 239). On March 12 McClellan sent a letter by Governor Dennison of Ohio which he marked ``Unofficial,'' reading in part as follows:
``I have just seen Gov. Dennison who has detailed to me the conversations he held with you yesterday and today.
``I beg to say. . . that I cordially endorse all that he said to you in my behalf, and. . . I thank you. . . for the official confidence & kind personal feelings you entertain for me. I believe I said to you some weeks since. . . that no feeling of self interest or ambition should ever prevent me from devoting myself to your service. I am glad to have the opportunity to prove it, & you will find that under present circumstances I shall work just as cheerfully as ever before & that no consideration of self will in any manner interfere with the discharge of my public duties. . . .'' (DLC-RTL).