Custer's company was attached to Gen. Phil Kearny's brigade, and that general detailed Custer as his aid-de-camp, and afterwards as assistant adjutant-general, which position he held till deprived of it by a general order prohibiting officers of the regular army from serving on the staffs of volunteer officers.
About this time he obtained leave of absence on account of ill health, and visited his sister, Mrs. Reed, at her home in Monroe, Michigan; and it is said that through her entreaties and influence he then gave up the habit of using strong drinks, which, in common with many of his fellow officers, he had acquired during his brief army life near Washington. Thenceforth, through the remainder of his life, he drank no intoxicating liquor.
Returning to the army in Feb. 1862, he was assigned to the 5th Cavalry, and when the enemy evacuated Manassas he participated in the advance on that place, and led the company which drove the hostile pickets across Cedar Run.
When the Army of the Potomac was transferred to the Peninsula, Custer's company was among the first to reach Fortress Monroe, and it then marched to Warwick. Here he was detailed as assistant to the chief engineer, on Gen. W.F. Smith's staff; he served in that capacity during the siege of Yorktown, and planned the earthwork nearest the enemy's lines. At the battle of Williamsburg, where he acted as aid-de-camp to Gen. Hancock, he effected the capture of a battle-flag—the first taken by the Army of the Potomac.
When the army was encamped near the Chickahominy River, late in May, Custer accompanied Gen. Barnard, the chief engineer of the army, on a
