In terms of the percentage losses suffered by both sides during the war, the Battle of Stones River at Murfreesboro, in Tennessee was by far the bloodiest, with the Union forces under William Stark Rosecrans losing 31% of its troops and the Confederate Army of Tennessee, under Bragg, losing more than a third of its manpower.
On December 26, Rosecrans’ Army of Cumberland departed from Nashville with a force of some 45,000 men. Facing him was Braxton Bragg with some 8,000 fewer infantrymen, but this imbalance was made up in part by the Confederate cavalry under Joseph Wheeler, a force that harried Rosecrans’ advance but could not prevent the Union army approaching the Confederate army astride the Stones River. Both sides planned to attack on the morning of December 31, but it was Bragg who took the initiative, launching a major attack against the Union left, forcing it to retreat some three miles.
Faced by the need to defend his left flank, Rosecrans abandoned his own scheme to attack the Confederate left, and it was only staunch defense in the center by Philip Sheridan that prevented the day turning into a rout of the Union army. Sheridan’s action, however, came at a high price as he lost almost one-third of his men killed or injured. With the Union defensive line now altered, Bragg identified the Round Forest as the pivotal point of the Union defense, ordering his forces, under John C. Breckinridge, to attack. By the end of the day’s action, neither side could claim victory, although the balance appeared to have swung in the Confederate’s favor.