Which Civil War general was nicknamed the "Rock of Chickamauga"?

George Henry Thomas (July 31, 1816 – March 28, 1870) was a United States Army officer and a Union general during the American Civil War. He was one of the principal commanders in the Western Theater.

Even though he was from Virginia, he remained loyal to the United States after the secession of his home state.

He won one of the first Union victories in the war, at Mill Springs in Kentucky, and served in important subordinate commands at Perryville and Stones River. His stout defense at the Battle of Chickamauga in 1863 saved the Union Army from being completely routed, earning him his most famous nickname, "the Rock of Chickamauga." He followed soon after with a dramatic breakthrough on Missionary Ridge in the Battle of Chattanooga. In the Franklin–Nashville Campaign of 1864, he achieved one of the most decisive victories of the war, destroying the army of Confederate General John Bell Hood, his former student at West Point, at the Battle of Nashville.