Explanation: The Confederate army wanted to destroy Kentucky Union sympathizers in the state.
Like Western Virginia, mountainous East Tennessee contained few slaves, and its population strongly opposed secession. While the overall vote in the state was more than 2-to-1 in favor of secession, East Tennesseeans voted by almost as great a margin against it. Within days of the referendum, a convention of East Tennesseeans met at Greeneville to discuss ways of resisting secession and firmly declared their loyalty to the Union and the Constitution.
Despite their talk of self-determination, Confederate authorities saw the East Tennesseeans as insurrectionists and move rapidly and forcefully to put them down by sending troops into the region. To command those troops, Pres. Jefferson Davis appointed former Nashville newspaper editor Felix K. Zollicoffer. Beyond a year's stint as a militia lieutenant during the 2nd Seminole War, Zollicoffer did not have any military background, but he was prominent in Whig Party politics an as such had originally mildly opposed secession. He seemed an ideal choice to supress and perhaps win over the antisecessionists of East Tennessee. As Kentucky was nuetral and would not permit transit of troops from either side, it appeared Zollicoffer would face nothing more than poorly trained and disorganized insurrectionists.
That changed when in early September Kentucky's neutrality ceased, and the entire northern boundary of Tennessee became exposed to possible invasion. Zollicoffer promptly advanced his forces to Cumberland Gap in the southeastern corner of Kentucky. Several weeks later, he advanced to Mill Springs, on the southeastern bank of the upper Cumberland River about 100 miles westnorthwest of Cumberland Gap. There he established a number of outposts along the river. Using ferryboats, he also established a foothold and large garrison at Beech Grove, on the northwest bank of the Cumberland River opposite Mill Springs, in early December. Too late to prevent the move, Zollicoffer's department commander, Gen. Albert S. Johnson, advised against crossing to the north bank of the Cumberland.
Meanwhile, Lincoln was eager to support any southern Unionists, whom he mistakenly thought formed the true majority of the South. In October, he began urging his generals to advance toward Cumberland Gap and East Tennessee, not only to aid the Unionists there but also to take possession of the strategic Virginia & Tennessee Railroad. Doing so, however, was extremely difficult, as the terrain was rough, the roads few and poor, and the problems of supplying an advancing army almost insurmountable. The task fell to Brig. Gen. Don C. Bell, a commander of the Union Department of the Ohio, headquartered in Louisville, Kentucky.
While Buell, never a fast mover, worried about the practical difficulties of getting troops to East Tennessee, the East Tennesseeans ran out of patience. On November 8th, they began an uprising against Confederate rule, burning important bridges and skirmishing with Confederate troops. Confederate authorities eventually succeeded in suppressing the uprising and hanged a number of its participants as rebels.
Meanwhile, Buell's troops were finally on the move. A brigade under Brig. Gen. Albin Schoepf advanced southeastward through Kentucky and by early December occupied Somerset, a town 25 miles northwest of Mill Springs, and began skirmishing with Zollicoffer's patrols. At about the same time another brigade, commanded by Col. James Garfield, moved farther east than Schoepf's troops and in early January routed a Confederate brigade under Brig. Gen. Humphrey Marshall at the Battle of Middle Creek near Prestonburg, Kentucky. Buell ordered an additional brigade under Brig. Gen. George H. Thomas to join Schoepf and attack Zollicoffer at Beech Grove.
More or less simultaneously, Maj. Gen. George B. Crittenden arrived at Mill Springs, dispatched by Jefferson Davis to supervise Zoliicoffer. He realized that Zollicoffer's position was extremely hazardous, as most of his forces were at Beech Grove and could not retreat back across the Cumberland River except by the long and laborious process of crossing on small ferryboats. With superior Union forces approaching, Crittenden decided that their only hope was to advance and catch Thomas' force before it could unite with Schoepf's. On the rainy night of January 18th, 1862, Crittenden and Zollicoffer marched their troops northward 6 miles to Thomas' position at Logan's Crossroads.
The Confederates attacked on the morning of the 19th. Recovering from their initial surprise, Thomas' troops rallied and dramatically routed the small Confederate army. Becoming confused in the mist and rain, Zollicoffer blundered into Union lines and was shot dead. The Confederates abandoned much of their equipment in getting back across the river at Mill Springs. The battle, known by varios names but most often as Mill Springs, involved about 4,000 men on each side. Union casualties totaled 261 men and Confederate, 531. Union morale in uncertain Kentucky got an important boost, and Crittenden's army was temporarily rendered all but completely incapable of further combat. The constraints of supply, however, prevented the Union army from following up its victory with a direct advance into East Tennessee.