later called "J. K.", was born on November 18, 1861, while Eli was serving in the military during the American Civil War. Career American Civil War service In 1861, a few months after the start of the American Civil War, Lilly enlisted in the Union Army. He joined the 21st Indiana Infantry Regiment and mustered into service on July 24. Lilly was commissioned as a second lieutenant on July 29, 1861. On August 3, the 21st Indiana reached Baltimore, Maryland, where it remained for several months. Lilly resigned his commission in December 1861 and returned to Indiana to form an artillery unit. In early 1862 Lilly actively recruited volunteers for his unit among his classmates, friends, local merchants and farmers. He had recruitment posters created and posted them around Indianapolis, promising to form the "crack battery of Indiana". His unit, the 18th Battery, Indiana Light Artillery, was known as the Lilly Battery and consisted of six, three-inch ordinance rifles and 150 men. Lilly was commissioned as a captain in the unit. The 18th Indiana mustered into service at Camp Morton in Indianapolis on August 6, 1862, and spent a brief time drilling before it was sent into battle under Major General William Rosecrans in Kentucky and Tennessee. Lilly's artillery unit was transferred to the Lightning Brigade, a mounted infantry under the command of Colonel, later General, John T. Wilder on December 16, 1862. Lilly was elected to serve as the commanding officer of his battery from August 1862 until the winter of 1863, when his three-year enlistment expired. His only prior military experience had been in a Lafayette, Indiana, militia unit. Several of his artillerymen considered him too young and intemperate to command; however, despite his initial inexperience, Lilly became a competent artillery officer. His battery was instrumental in several battles, including the Battle of Hoover's Gap in June 1863 and in the Second Battle of Chattanooga and the Battle of Chickamauga in August and September 1863. In 1864, when Lilly's term of enlistment ended, he resigned his commission and left the 18th Indiana. Lilly joined the 9th Indiana Cavalry (121st Regiment Indiana Volunteers) and was promoted to major. At the Battle of Sulphur Creek Trestle in Alabama in September 1864, he was captured by Confederate troops under the command of Major General Nathan B. Forrest and held in a prisoner-of-war camp at Enterprise, Mississippi until his release in a