Early in the war, the Lincoln administration knew well the importance of keeping the border state of Kentucky in the Union. Any Rebel armies operating successfully there could encourage secessionist sympathies. In late 1861, a Confederate force of around 6,000 men under Brig. Gen. Felix Zollicoffer encamped for the winter near Mill Springs, on the Cumberland River in the southeast corner of the state just north of the Tennessee border and close to the strategic Cumberland Gap. A Union force under Brig. Gen. George H. Thomas concentrated in the area and had moved to Logan's Crossroads by January 17th, 1862. Learning of the gathering Federal army, the Confederate area commander Maj. Gen. George B. Crittenden ordered Zollicoffer to give them battle. Zollicoffer's men attacked on January 19th in the early morning mist and rain, and initially gained success against the Yankee regiments. Zollicoffer was killed as he conducted a reconnaissance on a road in front of his men. The sudden death of their commander and heavy fire from the Federals caused the center of the Confederate line to fall back momentarily in confusion. The fighting raged at close quarters for over an hour until Thomas ordered the Union line to advance, overwhelming the Confederates who fled the field in disorder. The Federal victory at Mill Springs, the first significant Union victory of the Civil War, not only helped bolster sagging Northern morale but also helped to keep Kentucky more solidly in Union control.