Washington, and directed General Halleck to make me a detailed report.*

It has just been received, and I send it for your information. Please return it, that it may be recorded or filed in the archives of the Department.

Yours, truly,

EDWIN M. STANTON.

[Inclosure.]

WASHINGTON,

May 18, 1863.

Hon E. M. STANTON,

Secretary of War:

SIR: In compliance with your verbal directions of yesterday, to ascertain the number of troops which could be spared from the Department of Washington to re-enforce the Army of the Potomac in case of necessity, I have the honor to report as follows:

The whole number of troops for duty in this department is.................................................... 32,982

Deduct those in camps of convalescents and distribution.......................................... 1,177

---------

And we have for military duty......................... 31,805

These are distributed as follows:

Garrison of Fort Washington............................. 118

Guarding railroad to Baltimore.......................... 1,530

Guarding Potomac Rive to the Monocacy................... 1,177

Garrisons of forts north of the Potomac................. 5,329

Garrisons of forts south of the Potomac................. 5,988

Cavalry division for scouts, &c......................... 3,739

City guards of Washington and Alexandria................ 5,324

---------

23,205

This leaves under General Abercrombie a movable force of about 8,600. This movable division is now guarding the quartermaster's wood-cutters near Vienna, picketing the line of the Bull Run and the Occuquan, and guarding the railroad from Alexandria to Cedar Run. The forces on this railroad connect with General Hooker's outer line of pickets.

If the Army of the Potomac or its cavalry should operate on the Upper Rappahannock or Rapidan, the preservation of this line of railroad is important for forwarding supplies. If the movement should be entirely below the junction of the Rapidan and Rappahannock, this road should not be held.

The Secretary will remember the number of troops deemed necessary for the defense of Washington by the corps commanders when the Army of the Potomac left to operate upon the Peninsula. The Board of Defense, ordered by the War Department in October last, reported that the line of works (37 miles in length) required for their defense a force of 25,000, besides a force of 3,000 cavalry, for scouts and outpost duty. These estimates do not include the city garrisons for guarding the public stores and buildings, and for police duty. Moreover these estimates are based on the supposition that the proposed works are completed, whereas many of them are still incomplete. By comparing the estimates of the corps commanders of the Army of the Potomac and of the Board of Defense with the foregoing statement, it will be seen that the troops now available for the Defenses of Washington, exclusive

---------------

*See also Heintzelman to Halleck, May 17, p. 499.

---------------