In July 1864, a portion of the XIX Corps, including the 8th Vermont, was transferred to the eastern theater of the war. They arrived at Fortress Monroe just in time to join the VI Corps in the Shenandoah Valley, and participate in Major General Philip Sheridan's campaign against the Confederacy's Jubal Early. Thomas commanded the 2nd Brigade, 1st Division from October 15 to October 24, and again from November 1 to December 3, which included the 8th Vermont, 12th Connecticut, 160th New York and 47th Pennsylvania infantry regiments. During this period, the 8th Vermont participated in the Battle of Opequon, Battle of Fisher's Hill, Battle of Cedar Creek, and Newton, Virginia. In 1892 he received the Medal of Honor for "distinguished conduct in a desperate hand-to-hand encounter, in which the advance of the enemy was checked," at Cedar Creek on October 19, 1864.