Late in 1861, Confederates formed a defense line from the Big Sandy Valley in east Kentucky through Cumberland Gap, Mill Springs on the Cumberland River, Bowling Green on the L&N Railway, to Columbus, Kentucky, on the Mississippi River to block Union occupation of strategic points in Kentucky and Tennessee, maintain rail shipments of vital supplies from Virginia to the south and west, and prepare bases for future offensives through Kentucky and Ohio that would divide eastern and western Union states. In November 1861, Brig. Gen. Felix K. Zollicoffer built Confederate bases at Mill Springs and across the Cumberland at Beech Grove as part of that plan, and Maj. Gen. George B. Crittenden took command on December 13, 1861. On January 11, 1862, Union forces under Brig. Gen. George H. Thomas started from Lebanon, Kentucky, to join Federals under Brig. Gen. Albin Schoepf at Somerset and attack the Confederate base at Mill Springs. On January 19, Gen. Crittenden moved out with his Confederate troops to prevent Gen. Thomas's forces from joining the U.S. army at Somerset. In the first hour of the Battle of Mill Springs, Gen. Zollicoffer was killed, throwing his regiments into confusion. Gen. Crittenden rallied them and the battle continued for three hours, but United States reinforcements arrived and the Confederates retreated, fighting all day to reach the river. They evacuated camp during the night and withdrew into Tennessee. Confederate casualties were 125 killed, 309 wounded, and 99 missing; United States casualties were 39 killed and 207 wounded. The Confederates abandoned a large quantity of supplies, as well as 150 wagons and more than 1,000 horses and mules. Also called Logan’s Cross Roads or Fishing Creek, the battle opened the way for a Union advance into eastern Tennessee, though lack of provisions, bad roads, and the difficulty of crossing the river made that advance impractical. Gen. Thomas's command then joined Gen. Buell's Union force in the move on Nashville. This victory at Mill Springs, together with the defeat of Brig. Gen. Humphrey Marshall by Col. James A. Garfield in the Big Sandy Valley, broke the right section of the Confederate defense line and began a series of events that brought Union control of Kentucky and the upper Mississippi River in the first year of the war.