George Henry Thomas
Unlike his fellow Virginian Robert E. Lee, George Thomas remained loyal to the Union. During Nat Turner's bloody slave revolt, Thomas had led his family to safety and subsequently attended West Point (1840). A veteran of the Seminole and Mexican wars and an artillery and cavalry instructor at the academy, he was a major in the 2nd, soon to be the 5th Cavalry at the time of the secession crisis.
His war assignments included: lieutenant colonel, 2nd Cavalry (April 25, 1861); colonel, 2nd Cavalry (May 3, 1861); commanding 1st Brigade, in the 1st Division, Department of Pennsylvania (June-July 25,1861), in the Department of the Shenandoah July 25-August 17, 1861), and in Banks' Division, Army of the Potomac (August 17-28, 1861); brigadier general, USV (August 3,1861); commanding Camp Dick Robinson, Ken., Department of the Ohio (October-December 2, 1861); commanding lst Division, Army of the Ohio (December 2, 1861 - April 30,1862 and June 10 - September 29,1862); major general, USV (April 25,1862); commanding Army of the Tennessee (April 30-June 10, 1862); second in command of the Army of the Ohio (September 29-October 24, 1862); commanding Centre, 14th Corps, Army of the Cumberland (November 5, 1862 - January 9, 1863); commanding the corps January 9 - October 28,1863); brigadier general, USA (October 27,1863); commanding the army (October 28, 1863 - September 26, 1864); commanding Department of the Cumberland (October 28, 1863 June 27, 1865); and major general, USA (December 15, 1864).
After brief service in the East, Thomas was sent to Kentucky and commanded at Mill Springs. After arriving too late for the fighting at Shiloh, he commanded the Army of the Tennessee, replacing Grant who was shelved by being made second in command to Halleck. After participating in the slow drive on Corinth, Thomas returned to Kentucky and fought at Perryville and later at Stones River and in the Tullahoma Campaign. At Chickamauga, after most of the army had fled the field, Thomas stubbornly held out on the second day at Snodgrass Hill, earning the nickname "The Rock of Chickamauga."
After the defeat the army was besieged at Chattanooga, and Grant was promoted to overall command in the West and sent with reinforcements. He was given duplicate orders, one leaving General Rosecrans in command of the Army of the Cumberland and the other giving Thomas the post. Grant chose the latter although he resented Thomas for being replaced after Shiloh. Thomas' men broke through the Confederate lines at Missionary Ridge and later took part in the capture of Atlanta.
With Hood's Army of Tennessee threatening Tennessee, in Sherman's rear, Thomas was detached with two corps to deal with him. This was effectively the end of the Army of the Cumberland. After being briefly besieged at Nashville, Thomas, who was about to be removed for being too slow, attacked and routed the rebels. For this, one of the most decisive battles of the war, Thomas became one of 13 officers to receive the Thanks of Congress. Hood's command was no longer a real threat to anyone. With most of his forces sent to other theaters of operations, Thomas remained in command in Tennessee until 1867, when he was assigned to command on the Pacific coast until his death in 1870. (McKinney, Francis F., Education in Violence: The Life of George H. Thomas and the History of the Army of the Cumberland)
Source: "Who Was Who In The Civil War" by Stewart Sifakis