Civil War Union Army Officer. He began his Civil War service with a commission of Captain in the 79th Pennsylvania Volunteer Infantry on September 5, 1861, and was mustered in as commander of the regiment's Company B. He led the company when his regiment was assigned to Army of the Ohio, and sent to counter Confederate movements in Kentucky and Tennessee. He participated in the pursuit of Confederate General Braxton Bragg's forces that culminated in the October 8, 1862 Battle of Perryville, Kentucky. However, the day before the battle the 79th Pennsylvania's original Lieutenant Colonel, John H. Duchman, resigned, and David Miles, as senior captain, performed as acting Lieutenant Colonel in the battle. A few days later the move was made permanent, and he was promoted to Lieutenant Colonel, with his commission back-dated the day of the Perryville fight. The next pitched battle the regiment participated in, the December-January 1862-1863 Battle of Murfreesboro, saw him assume command of the regiment when its Colonel, Henry A. Hambright, was elevated to brigade command for a time. Returning to his regular duties after the battle, he served in the Army of the Cumberland's operations in Tennessee, still pursuing the forces of General Braxton Bragg. In the initial stages of the September 19, 1863 Battle of Chickamauga, Lieutenant Colonel Miles and a detachment of 20 men were separated from the main body of troops and were swallowed up by onrushing Confederates. Confined to the infamous Libby Prison in Richmond, Virginia, he was one of the 109 Union officers who participated in the February 9, 1864 prison escape orchestrated by Colonel Thomas E. Rose of the 77th Pennsylvania Infantry. While many officers were eventually recaptured, Lieutenant Colonel Miles was one of a relative handful to successfully return to Union lines. After he rejoined his regiment, he became the senior officer in his brigade, and eventually assumed its command. He led the brigade in major General William T. Sherman's March to the Sea, and in the drive through the Carolinas. At the March 19, 1865 Battle of Bentonville, North Carolina, he was wounded while directing his men against the attacking Confederates. His promotion blocked by Colonel Hambright's commission, he was nonetheless brevetted Colonel, US Volunteers on March 13, 1865. He served through the end of the conflict, and was honorably mustered out with the 79th Pennsylvania on July 12, 1865.