The Union victory at Mill Springs, along with the other engagements noted, probably spelled defeat for the Confederacy. It was early in the war, and it may not have been apparent at that time, but by successfully busting the Confederate defensive line across southern Kentucky and northern Tennessee, the ultimate outcome of the war was set in stone. My opinion.The map above indicates the geographic significance of the tiny battle; the Confederate force at right labeled Crittenden was the anchor of Confederate General Albert Sidney Johnston's line which stretched entirely across the state of Kentucky from the bastion of Columbus in the west to the Cumberland Gap in the East, with Johnston's headquarters near the center in Bowling Green. Once the Confederate right was defeated and driven back at Mill Springs, it was followed quickly by Maj. Gen. Ulysses S. Grant's advance into Tennessee and capture of Forts Henry and Donelson in early February. This collapsed Johnston's line, causing the evacuation of Columbus, Bowling Green, and the entire state of Kentucky, without which President Abraham Lincoln said the war could not be won.