The First Brigade was detached at Gettysburg on July 4, and rejoined the division at Boonsborough on the 12th; was again detached at Harper's Ferry on the 19th, and rejoined at Warrenton Junction on the 28th. The report of the operations of this brigade while detached is appended, marked B. *The Third Brigade, Colonel John I. Gregg, Sixteenth Pennsylvania Cavalry, commanding, was detached and sent in pursuit of the enemy on July 5, and rejoined the division on July 11, at Boonsborough, Md. The report of the operations of this brigade is appended, marked C. The three brigades of the division having been thus detached, division headquarters were on the 9th transferred to Boonsborough from Gettysburg. On the 14th, agreeably to instruction from the major-general commanding Cavalry Corps, I moved with the First and Third Brigades of the division to Harper's Ferry and at that point crossed the Potomac. On the road leading from Harper's Ferry to Charlestown, a force of the enemy's cavalry was met and quickly driven back upon Charlestown. This movement, with two brigades to the west side of the Potomac, had for its object interference with the enemy's line of communication between Winchester and the rover. Every preparation was made for carrying out fully the plan of sweeping the road between Winchester and Martinsburg, when a telegram from the major-general commanding Calvary Corps informed me that the entire rebel army had effected a crossing, and also that the Second Brigade of my division had been ordered to me. With the view of getting in rear of and on the flank of the rebels, on the 15th I marched with the First and Third Brigades to Shepherdstown. Finding the roads leading from that town to Winchester and Martinsburg both strongly picketed with infantry and cavalry, I halted to await the arrival of the Second Brigades, so that I might have sufficient force to advance upon either of these roads. On the 16th, the Second Brigade not having arrived, and from reconnaissances having ascertained that with the force with me I could not successfully advance, I determined to withdraw toward Harper's Ferry, and from thence operate on another route. At about noon, a few shots heard on the road leading to Winchester announced an attack on our pickets, Repairing to the front, I learned that an advance guard of the enemy's column had attacked our pickets. Seeing this advance party dismount to remove the fences and make preparations for an attack by the columns in rear, I at once placed the Third Brigade(Colonel Gregg's) in position to meet it. As was expected, the enemy attacked in large force, and brought to the assistance of their dismounted cavalry the fire of six pieces of artillery. Soon the engagement became very spirited. The Fourth and Sixteenth Pennsylvania and First Maine Regiment were principally engaged in my front; the Tenth New York on the right, covering the road leading to Martinsburg rad, the First Brigade was at the same time on the Martinsburg road, the First Brigade was placed on the south side of the town to hold the roads leading to Harper's Ferry and Charlestown, and also in position to be brought

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*See Report Numbers 348, p. 967

+See Report Numbers 355. p. 974

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