Robert and his family lived in Aurora, IN in 1860, where he worked as an attorney. In September, 1862, Terrill enlisted as a 1st Lieutenant with the 11th KY Cavalry, Co. E, in defense of the Union. He was captured during a battle in Hartsville, TN in December, 1862.
At this same battle, were the forces of the Confederate Ky 5th Cavalry, Company G. Robert Terrill's brothers: Cpt. George W. Terrill, Joshua Terrill, and Simeon Terrill, and a nephew James Berkshire, were all in this regiment at the time of his capture. Robert was released to the Union. He went on to report for duty at Camp Chase, OH in Jan-Feb. of 1863. His brother George was sent to Camp Chase as a prisoner only five months after Robert's transfer.
Robert resigned from the service May 7, 1863 and returned home, due to muscular problems, rheumatism and heart palpitations, cited by his regiment's surgeon.
He bought the Lawrenceburg Ferry after returning from the war. He was unable to make monthly payment to his ferryman, Maurice McNealy, who then placed a lien on the ferry. Terrill, in an agitated state, went to the ferry to settle the dispute with his employee. They exchanged gunfire; McNealy was wounded and Robert was killed. The court decided that McNealy acted in self-defense.