Numbers 579. Report of Colonel Thomas L. Rosser, Fifth Virginia Cavalry, of action at Aldie.

AUGUST 4, 1863.

CAPTAIN: The brigade leaving Piedmont, in Loudoun County, on the morning of June 17, I was ordered to withdraw my pickets after the column had passed, and followed in the rear, marching via Paris and Upperville. I arrived at Dover [near Aldie] about 12 or 1 o'clock. Finding the brigade going into camp, I received an order from Colonel Wickham, under whose command I had been temporarily placed, to move down the road and select a camp, make my men comfortable, &tc. I consequently did so, and, when I was just passing the brigade, I met the pickets running in, and the Yankees rapidly and closely pursuing them. I caused sabers to be drawn, and charged immediately, at the same time sending the information to the rear, to the colonel commanding. I drove the enemy upon his main body, which was in the town of Aldie. His sharpshooters got possession of the heights on my left, in the wood and behind the fences, and it was impossible for me to engage him further with the saber; consequently I deployed my sharpshooters to the front, under Captain R. B. Boston, and withdrew the regiment beyond the range of the enemy's rifles. As soon as this was done, he charged my skirmishers, who were doing terrible execution in his ranks, endeavoring to dislodge them, but, by a counter-charge, I gave them immediate relief. The enemy now showed considerable force, his flanks extending far beyond mine on the left, on the Snicker's Gap pike. His dismounted skirmishers had pressed upon mine until their fighting had become desperate and close. The most of the horses of my dismounted men had been killed, and the enemy, seeing that my force was small [the brigade had not yet gotten up], made a desperate effort to capture them, charging them in flank, right, and left. As soon as his intentions were made known, I charged the regiment which was threatening the right, drove them back, and the gallant Boston drove his assailants on the left back in confusion and dismay, after emptying many of their saddles. The enemy brought his artillery into position, but the brigade coming to my support, our own artillery replied briskly, and for a moment the fight between the cavalry became less vigorous. Each battery, the enemy's and our own, firing over my regiment, and having suffered several casualties from the latter, it became necessary for me to move from between the two, which I did promptly, but was compelled to take a position from which I could not support my line of skirmishers so well as before; and the re-enforcements sent from the brigade to them taking up a position considerably in their rear, and the remainder of the brigade being engaged on the left, on the Snicker's Gap pike, their condition became very critical. The enemy, greatly outnumbering us, appeared in force everywhere, and it became apparent that victory was the only means of escape. I ordered Boston to hold his position at all hazards, and nobly and faithfully did he obey. Onset after onset of the enemy he gallantly repulsed, until after the enemy had pressed beyond the left, overwhelmed his support, killed one of his lieutenants, wounded another