McKinley was still on General Hayes’ staff when the battle of Kernstown, July 24, 1864, was fought. Crook’s corps had been expecting an easy time when it appeared that the enemy was in force at Kernstown, about four miles from Winchester, where Crook’s troops were. There had been some misinformation regarding the Confederate General Early’s movements, and the force about to be met was that of Early, which outnumbered Crook’s corps three to one. When the battle began one of the regiments was not in position, and Lieutenant McKinley was ordered to bring it in. The road to the regiment needed was through open fields and right in the enemy’s line of fire. Shells were bursting on his right and left, but the boy soldier rode on. He reached the regiment, gave the orders to them, and at his suggestion the regiment fired on the enemy and slowly withdrew to take the position where they were assigned. It was a gallant act of the boy soldier, and General Hayes had not expected him to come back alive.
He distinguished himself for gallantry, for good judgment, and military skill at the battle of Opequan. He had been ordered to bring General Duval’s troops to join the first division, which was getting into the battle. There was a question of which route to take, and upon the choice depended the very existence of General Duval and his brave men. Lieutenant McKinley weighed the chances swiftly, decided instantly, and on his own responsibility pointed out the direction as he gave his superior officer’s command to move. The troops followed his instructions, and came up gallantly and in excellent style, with the smallest possible loss or injury. His own regiment, the Twenty-third Ohio, was less skillfully directed, and suffered the very severe loss of 150 men and officers.
The work accomplished on that day marked young Lieutenant McKinley as both modest and brave.
Early in 1863, William McKinley, Jr., was promoted to the rank of first lieutenant, but was retained on staff duty, as his superior ability, coolness and rare judgment made him invaluable to the regimental commander. That year the regiment saw service almost exclusively in West Virginia, engaged in the scouting duty which alone preserved that territory from falling into the possession of the enemy. It was a wearying year, trying on the men without giving them opportunity to share the glory that more active soldiering would have brought. They were marched east and west, north and south. It was a year of inaction, so far as achieving results were concerned. And in this severer test Lieutenant McKinley proved himself a soldier of the best ability. He kept up that esprit du corps throughout the regiment, without which it would have been ill prepared for service when the time for action came.