Tompkins was born in
Fort Monroe, Virginia, on September 12, 1830. Tompkins pursued private business interests until
enlisting as a
Private in the First Dragoons in January 1856, rising to the rank of
sergeant before his enlistment ended in January 1861. He served on the western frontier and was recognized for his performance at the
Second Battle of Pyramid Lake near
Pyramid Lake, Nevada, in June 1860. Tompkins received his commission as a 2nd lieutenant in the
2nd U.S. Cavalry Regiment in March 1861. It was in this unit that he gained fame for his heroism in action at the
Battle of Fairfax Court House (June 1861) while a 1st lieutenant, to which he was promoted on April 30, 1861. Tompkins was reassigned to the
5th U.S. Cavalry Regiment on August 3, 1861, and served as the regimental quartermaster. On April 24, 1862, he received a volunteer commission as colonel of the
1st Vermont Cavalry. He resigned his volunteer commission on September 9, 1862. During the war, he received brevets (honorary promotions) to major, lieutenant colonel, colonel and brigadier general. ==Medal of Honor citation==