The Chattanooga campaign was a series of maneuvers and battles in October and November 1863, during the American Civil War. Following the defeat of Maj. Gen. William S. Rosecrans's Union Army of the Cumberland at the Battle of Chickamauga in September, the Confederate Army of Tennessee under Gen. Braxton Bragg besieged Rosecrans and his men by occupying key high terrain around Chattanooga, Tennessee. Maj. Gen. Ulysses S. Grant was given command of Union forces in the West, now consolidated under the Division of the Mississippi. Significant reinforcements also began to arrive with him in Chattanooga from Mississippi and the Eastern Theater. On October 18, Grant removed Rosecrans from command of the Army of the Cumberland and replaced him with Major General George Henry Thomas.

William Starke Rosecrans was an American inventor, coal-oil company executive, diplomat, politician, and U.S. Army officer. He gained fame for his role as a Union general during the American Civil War. He was the victor at prominent Western Theater battles, but his military career was effectively ended following his disastrous defeat at the Battle of Chickamauga in 1863.