The Battle of Chickamauga was fought on September 19–20, 1863, in northwestern Georgia during the American Civil War. It was the most significant Confederate victory in the Western Theater and the second-bloodiest battle of the war after Gettysburg, with about 34,000 total casualties. Confederate forces under General Braxton Bragg clashed with Union troops led by Major General William Rosecrans, who had been pushing south after capturing Chattanooga, Tennessee. On the second day of fighting, a gap in the Union line allowed Confederate General James Longstreet’s forces to launch a massive assault, driving much of the Union army from the field. However, Union General George H. Thomas held firm with a portion of the army, earning him the nickname “The Rock of Chickamauga.” Despite the Confederate victory, their failure to retake Chattanooga allowed the Union to later launch campaigns that opened the Deep South to invasion.