HEADQUARTERS U. S. FORCES,
Poolesville, Md., July 16, 1864--7 a. m.

GENERAL: Your dispatch of yesterday, by Captain Farrar, of my staff, was received toward evening, and about the same time I received intelligence through my own couriers from General Hunter's command, and also a dispatch from General Howe, at Harper's Ferry, where General Hunter had just arrived. A little later I received the dispatch of Colonel Chipman, of General Hunter's staff, to the Secretary of War, from which and from other information I learned that General Sullivan, with some 7,000 infantry and 2,000 cavalry, crossed the Potomac at Knoxville, near Berlin, and was moving on Leesburg via Hillsborough. Fearing that he might meet the enemy in too strong force for his command, I have put the force here in motion for Leesburg, crossing at White's Ford, and have instructed General Ord to move as rapidly as practicable to the same point, crossing at Young's Island, about one and a half miles below Edwards Ferry.

The troops of the Nineteenth Corps reached this point late in the afternoon of yesterday, and constitute, with the two divisions of the Sixth Corps, the force with which I am moving on Leesburg. General Ord's command will not probably reach that point before all day to-morrow.

The necessity for supporting General Sullivan's movement renders it necessary to move in advance of a portion of the trains not yet up, but I think they will be sufficiently covered by the general movement and the small force left for their protection.

From the information gained here from Union citizens well acquainted with the country on the other side of the river I apprehend that it will be impossible to subsist to any extent on the country, with the exception of forage, everything having been pretty much swept off by the enemy.

My headquarters will be at Leesburg to-night.

Very respectfully, your obedient servant,

H. G. WRIGHT,

Major-General, Commanding.

Major General H. W. HALLECK,

Chief of Staff, &c.

HEADQUARTERS U. S. FORCES,
Clark's Gap, three miles beyond Leesburg,

July 17, 1864--7.30 p. m.

GENERAL: I have the honor to acknowledge the receipt of your dispatch of to-day. I reached here late last evening, and during the night opened communication with General Crook, who, with Sullivan's division, Mulligan's brigade, and some 2,000 cavalry, encamped at Purcellville, about six miles from this point. I at once instructed General Crook to follow up the enemy with his cavalry, supported by infantry, but as nothing has been heard from the detachment it is inferred that the enemy continued his retreat. Moving rapidly I struck his rear guard of cavalry at Leesburg, but he retreated before the head of the infantry column got up, taking the direction of Snicker's Gap. The cavalry of General Crook's command, under General Duffie, more fortunate than the rest, struck the rear of the