Only one Union regiment at Mill Springs, the 9th Ohio, had much combat experience

While the center of the Confederate line briefly fell back in confusion due to the sudden death of Brig. Gen. Felix Zollicoffer and heavy fire from Fry's regiment. When Thomas arrived on the scene, he gave the order for the 9th Ohio to go forward while the 2nd Minnesota continued to fire heavily from the front. The battle was won when the 9th Ohio turned the Confederate left flank. The Confederate soldiers broke and fled in disorganized disarray back toward Mill Springs. This showed the strength of the 9th Ohio.

There were numerous veterans of the German 1848 uprisings in Europe in the 9th Ohio, which was primarily composed of German-speaking Cincinnati soldiers. The Battle of Mill Springs would involve a significant contribution from the 9th Ohio. The 9th, under the command of Maj. Gustave Kammerling launched a daring and effective bayonet charge that contributed to the Confederate forces' loss. Kammerling reportedly said, "If it gets too hot for you, close your eyes my soldiers - Forward!" as the 9th Ohio advanced with bayonets poised.