George Thomas

Thomas was a native Virginian, born in 1816, who decided to fight for the Union in the Civil War. Thomas graduated from West Point in 1840, served in the Mexican War, and was a cavalry officer prior to the war. He commanded a brigade under General Robert Patterson in the First Manassas campaign, and was promoted to brigadier general in August, 1861. He saw action at Shiloh, Corinth, and Stone's River, but won fame at Chickamauga where he earned the nickname "Rock of Chickamauga" for holding his ground while the rest of the Union army retreated. After Chattanooga, Thomas commanded the Army of the Cumberland which marched to Atlanta with William T. Sherman and stopped John B. Hood's invasion of Tennessee at Nashville. He commanded the Department of the Tennessee until 1867. George Thomas died of a stroke in 1870.
Source: "Generals in Blue" Warner, Ezra J.