May 6 the Regiment was assigned to Wilder's Brigade, Reynolds' Division, Fourteenth Corps, composed of Seventeenth and Seventy-second Indiana, and Ninety-Eighth and One Hundred and Twenty-third Illinois. They were mounted, and armed with Spencer rifles--seven shooters. Did scouting and patrol duty for a month or so.

June 24 this Brigade led the advance of Rosecrans' army in its movement from Murfreesboro, the Seventeenth Indiana being in advance and the One Hundred and Twenty-third Illinois next. These two Regiments moved out from Murfreesboro long before daylight on the morning of the 24th, in a drenching rain, and by daylight encountered the rebel videttes. From that moment the two Regiments broke into a gallop and kept up the run. The farther they went the larger the rebel force of cavalry kept growing before them, but the rapid pace gave the enemy no time to form, until about 9 o'clock, in the morning by which time the two Regiments had advanced to and seized Hoover's Gap, a plan of great natural strength, but they were confronted here with twenty times their own number of infantry, well supplied with artillery to occupy this Gap, and their supporting forces were at least ten miles in the rear, floundering along through the mud and rain. But the rapidity and audacity of the movement saved them, for the enemy, supposing the force was a large one, checked there advance in column, deployed the force in two lines, brought up there artillery and opened a terrific artillery fire, at the same time sending out reconnoitering parties on the Federal flanks, but as soon as the gap was seized, couriers had been dispatched back to Wilder, informing him of the situation, and before the enemy had satisfied himself of the force in his front, the other Regiments of the Brigade arrived, and with it the battery of Captain Lilly, (Indiana) his guns having been hauled the last mile by men of the Brigade. Lilly's horses having given out with their long run through the muddy roads.

These reinforcements checked the enemy still more, but by 2 P. M. they made a determined attack along the whole line and on both flanks, but the seven shooting Spencer rifles proved effective in repelling it, and before another could be made the head of the Infantry of Rosecrans' army began to arrive, and Hoover's Gap was held without further contest, the enemy withdrawing in the night. The Regiment lost several killed and wounded in this affair.