HEADQUARTERS ARMY OF THE POTOMAC, October 15, 1863-10. 30 a. m.

Commanding Officer Fifth Corps:

The major-general commanding directs me to inform you that Brigadier General Rufus King has been ordered to report to you with his division at Fairfax Court-House. Such of his troops as are guarding the railroad (with the exception of those at Fairfax Station) will remain on that duty.

Very respectfully, &c.,
A. A. HUMPHREYS,

Major-General, and Chief of Staff.

HEADQUARTERS ARMY OF THE POTOMAC, Centerville, October 15, 1863-12 m. (Received 1. 45 p. m.)

Major General H. W. HALLECK,

General-in-Chief:

Generals Warren and Sykes were successfully withdrawn last night, and the army is now at Union Mills, Centerville, Chantilly, and Fairfax Court-House, awaiting the movements of the enemy. The cavalry is out on the flank and the front, endeavoring the ascertain the position and movements of the enemy. General Warren engaged yesterday Heth's division, of Hill's corps, inflicting serious injury on it, taking 5 guns and 450 prisoners. Among the prisoners are soldiers just from Charleston. The reports of teh prisoners are that Hill's and Ewell's corps, re-enforced to a reported strength of 80,000, are advancing on me, their plan being to secure the Bull Run field in advance of me. They started five days ago with seven days' rations with the men and large supply trains.

I am unable to surmise whether Lee will await opening his communication with Gordonsville, or whether he will continue his advance. In the latter case, I suppose he will turn me again, probably by the right, with his back to the mountain, in which case I shall either fall on him or retire nearer Washington, according as his movements indicate the probability of his being able to concentrate more rapidly than I can. I have ordered General King, with such of his troops as are at Fairfax Court-House and Station, to report to Major-General Sykes, Fifth Corps.

GEO. G. MEADE,

Major-General, Commanding.

UNION MILLS, October 15, 1863.

General HUMPHREYS,

Chief of Staff:

The enemy are reconnoitering the fords with cavalry and artillery, not in large force. A rapid crossing of our cavalry at Mitchell's Ford would break it up.

WM. H. FRENCH,

Major-General.