[24][b] McKinley's regiment suffered many casualties, but the Army of the Potomac was victorious and the Confederates retreated into Virginia.[24] McKinley's regiment was detached from the Army of the Potomac and returned by train to western Virginia.[25]

Shenandoah Valley and promotion
McKinley in 1865, just after the war, photograph by Mathew Brady
While the regiment went into winter quarters near Charleston, Virginia (present-day West Virginia), McKinley was ordered back to Ohio with some other sergeants to recruit fresh troops.[26] When they arrived in Columbus, Governor David Tod surprised McKinley with a commission as second lieutenant in recognition of his service at Antietam.[26] McKinley and his comrades saw little action until July 1863, when the division skirmished with John Hunt Morgan's cavalry at the Battle of Buffington Island.[27] Early in 1864, the Army command structure in West Virginia was reorganized, and the division was assigned to George Crook's Army of West Virginia.[28] They soon resumed the offensive, marching into southwestern Virginia to destroy salt and lead mines used by the enemy.