Thomas attained the rank of major general during the Civil War. His finest hour came at the Battle of Chickamauga in the autumn of 1863, where he commanded XIV Corps, when he disobeyed orders to retreat and held against an overwhelming Confederate assault, allowing the defeated Army of the Cumberland to retreat in an orderly fashion rather than be routed. After the battle but before the subsequent Battle of Chattanooga which ended Braxton Bragg's offensive campaign, Thomas was promoted to commander of the Army of the Cumberland. Still in this capacity, he served as second-in-command to William Sherman during the Atlanta Campaign of the spring and summer of 1864. (Sherman's forces on this campaign consisted of the Armies of the Cumberland, the Ohio, and the Tennessee.) Following the fall of Atlanta, John Bell Hood broke away from the city and cut Sherman's lines of communication. Sherman elected to lead most of his force campaigning in a northeasterly direction without being in contact with his superiors (his storied March to the Sea), but he dispatched Thomas northwest to engage Hood with a small force consisting of IV Corps, XXIII Corps, and four divisions of cavalry. Thomas and Hood raced for the city of Nashville, Tennessee, where Thomas was to receive reinforcements. Thomas dealt Hood crippling losses at the Battles of Franklin and Nashville in December 1864, effectively destroying the last Confederate army remaining in the field.
After the war, Thomas was given several assignments as military governor of various occupied secessionist territories. In these capacities he aggressively protected freedmen from abuse, suppressed the Ku Klux Klan, and set up commissions to arbitrate labor disputes on the grounds that the local courts were not capable of ruling impartially. In 1869 he requested a transfer and was named commander of the Division of the Pacific, commanding US Army forces on the West Coast. The following year he died of a stroke at his headquarters in the Presidio of San Francisco while writing a letter defending his reputation against a political rival.
George Thomas in "Lee at the Alamo"Edit
Major George Thomas was the second-ranking U.S. Army officer in San Antonio after Lieutenant Colonel Robert E. Lee. Thomas served as Lee's second-in-command during the siege of the Alamo by Texan and Confederate forces. Thomas made an energetic and effective lieutenant, despite one breach of discipline: Thomas, a very staunch Unionist despite his Virginian home, favored dealing aggressively with Southern secessionists, a position toward which President James Buchanan showed no inclination. Thomas was openly critical of Buchanan in defiance of the US Army's prohibition against its personnel publicly expressing political opinion, even after Lee sharply rebuked him for indiscreet speech.
After the Department of Texas surrendered the Alamo and was issued safe passage to territory under effective US control, Thomas had no trouble deciding to remain in the Army and to accept a combat assignment against the Confederacy as soon as his exchange could be arranged. This was in marked difference to Lee, who, despite his experiences at the Alamo, agonized over where his loyalties lay after his and Thomas's home state of Virginia seceded.
- Doubting George, a POV character in the The War Between the Provinces, who is heavily based on George Thomas.
| Military offices|
|Commander of the Army of the Cumberland|
October 19, 1863–August 1, 1865
| Succeeded by|