On the 8th of March, 1862, the President directed, by the following order, the organization of the active portion of the Army of the Potomac into four army corps, and the formation of a fifth corps from the divisions of Banks and Shields.

The following is the next of the President's order:

PRESIDENT'S GENERAL WAR ORDER,
EXECUTIVE MANSION,

Numbers 2.
Washington, March 8, 1862.

Ordered, 1. That the major-general commanding the Army of the Potomac proceed forthwith to organize that part of the said army destined to enter upon active operations (including the reserve, but excluding the troops to be left in the fortifications about Washington) into four army corps, to be commanded according to seniority of rank, as follows:

First Corps to consist of four divisions, and to be commanded by Major General I. McDowell.

Second Corps to consist of three divisions, and to be commanded by Brigadier General E. V. Sumner.

Third Corps to consist of three divisions, and to be commanded by Brigadier General S. P. Heintzelman.

Fourth Corps to consist of three divisions, and to be commanded by Brigadier General E. D. Keyes.

2. That the divisions now commanded by the officers above assigned to the commands of army corps shall be embraced in and form pat of their respective corps.

3. The forces left for the defense of Washington will be placed in command of Brigadier General James S. Wadsworth, who shall also be military governor of the District of Columbia.

4. That this order be executed with such promptness and dispatch as not to delay the commencement of the operations already directed to be undertaken by the Army of the Potomac.

5. A fifth army corps, to be commanded by Major General N. P. Banks, will be formed from his own and General Shields' (late General Lander's) divisions.

ABRAHAM LINCOLN.

The following order, which was made as soon as circumstances permitted, exhibits the steps taken to carry out the requirements of the President's War Order, Numbers 2:

GENERAL ORDERS,
HEADQUARTERS ARMY OF THE POTOMAC,

Numbers 151.
Fairfax Court-House, Va., March 13, 1862.

In compliance with the President's War Order, Numbers 2, of March 8, 1862, the active portion of the Army of the Potomac is formed into army corps, as follows:

First Corps, Major General Irvin McDowell, to consist for the present of the divisions of Franklin, McCall, and King.

Second Corps, Brigadier General E. V. Sumner; divisions, Richardson, Blenker, and Sedgwick.

Third Corps, Brigadier General S. P. Heintzelman; divisions, F. J. Porter, Hooker, and Hamilton.

Fourth Corps, Brigadier General E. D. Keyes; divisions, Couch, Smith, and Casey.

Fifth Corps, Major General N. P. Banks; divisions, Williams and Shields.

The cavalry regiments attached to divisions will for the present remain so. Subsequent orders will provide for these regiments, as well as for the reserve artillery, regular infantry, and regular cavalry. Arrangements will be made to unite the divisions of each army corps as promptly as possible.

The commanders of divisions will at once report in person, or, where that is impossible, by letter to the commander of their army corps.

By command of Major-General McClellan:

A. V. COLBURN,

Assistant Adjutant-General.

I add a statement of the organization and composition of the troops on April 1, commencing with the portion of the Army of the Potomac which went to the Peninsula, giving afterwards the regiments and batteries left on the Potomac and in Maryland and Virginia after April 1, 1862: