The 18th Indiana Light Artillery was recruited in response to Lincoln's call of July 2, 1862, for 300,000 volunteers to serve for three years. The battery, recruited from counties in west-central Indiana, consisted primarily of farmers (about 50%) and an unusually large number of college students. Over half of the 156 men were from Indiana, 26 were from other Northern states, 14 were from Southern states, and seven were from foreign countries. Eli Lilly was appointed by the governor to recruit, organize, and lead the battery. Lilly had been a chemist and pharmacist, and his only military experience was as a member of a militia unit in Lafayette, Indiana. Some of his men considered him too young and intemperate to command. He later remarked that he lived on whiskey, quinine, and tobacco while in the service. In the winter of 1863 Lilly left the battery to accept a colonel's appointment in the cavalry. He was later captured and paroled by Forrest at Sulphur Trestle in Alabama, and returned to civilian life to resume his career in pharmaceuticals.

    The battery was formed in August of 1862 at Camp Morton in Indianapolis, where the men elected their officers and NCOs. There they waited for their weapons and complained of not drilling. This changed on September 1 when they were issued six 3" Ordnance Rifles and supporting equipment, and were rushed off to war without any training or drill. The men had to move the guns, limbers, and caissons onto train cars by hand because no horses were available. This sudden departure was in response to Bragg's invasion of Kentucky. Fortunately, the untrained battery did not participate in any of the engagements of that campaign. After Bragg's retreat back into Tennessee, the battery had time to train and conduct gunnery practice. The cannoneers were surprised at the accuracy of their Ordnance Rifles; noting that two guns were able to hit a wheat sack hung on a fence at a range of about 3/4 mile.

    The 18th Indiana joined the Army of the Cumberland on January 6, 1863 (just after the Battle of Stone's River), and were assigned to Wilder's Infantry Brigade. During their ten-month assignment to this elite unit, the battery participated in some of their most notable engagements, including the Battle of Chickamauga. Wilder's Brigade was mounted and equipped with seven-shot Spencer repeating rifles, and was renowned as one of the best fighting brigades in the Army of the Cumberland. Because of their mobility and fire-power, the brigade and the 18th Indiana played a prominent role during Rosecrans' campaign against Chattanooga. It was during this time that two mountain howitzers were added to the battery's ordnance. These small guns were light enough to be carried by two pack mules, so were ideal for service in rough terrain; the guns became known among the cannoneers as the "jackass battery".

    During the Chattanooga campaign, the battery was engaged at Hoover's Gap, Poe's Tavern, and was the first Federal unit to fire on Confederate forts in Chattanooga. In the subsequent Chickamauga campaign, General Thomas began to realize that the Confederates were not in retreat when Wilder's Brigade and the 18th Indiana encountered serious Confederate resistance at Ringold, Georgia on September 11, 1863. As the armies converged on September 18, Wilder's Brigade and the battery prevented Bragg from turning the Federal flank by their defense of fords across Chickamauga Creek. Thus, for these units, Chickamauga was a three-day engagement rather than the two days usually attributed to the battle. On the second day of battle, the battery was heavily engaged at Viniard's Field. A well hidden monument now stands at the corner of this field where the battery stopped repeated Confederate charges with canister fire from the Ordnance Rifles and mountain howitzers. On the third day, Wilder's Brigade and the battery slowed Longstreet's breakthrough long enough for Thomas to form his corps for his famous Rock of Chickamauga stand. Wilder's Brigade and the battery were the last Federal units to leave the field.

    Much to the dismay of Captain Lilly the men, the 18th Indiana Battery was transferred to the 1st Cavalry Division of the Army of the Cumberland on November 17, 1863. The battery participated in a grueling cavalry campaign in east Tennessee with that division from November 1863 until April 1864. During this campaign they fought in four heavy skirmishes in which they suffered a number of killed and wounded and had one gun captured. In May, 1864, after refitting, the battery participated in Sherman's Atlanta Campaign. They fought in skirmishes and battles at Varnell's Station, Resaca, Cartersville, Lost Mountain, and Vining's Bridge, The First Section also participated in the disastrous cavalry raid south of Atlanta by General McCook . Both guns of the section were captured, but most of the men managed to escape and make their way back to Federal lines.

    After the fall of Atlanta, the battery was sent back to Nashville. They were sent with a cavalry force chasing Confederate General Lyon through Kentucky in December, 1864; thus missing the Battle of Nashville. In March, 1965, the 1st Cavalry Division and 18th Indiana were transferred to Wilson's cavalry corps, and participated in Wilson's Raid through Alabama and Georgia. During this raid, the battery fought in the skirmish at the Centerville Bridge, which prevented Generals Jackson and Chalmers from reaching Forrest and assisting him in the defense of Selma. The battery's last action came at Fort Tyler which defended a bridge across the Chattahoochee River at West Point, Georgia. Here a detachment silenced a 32 pounder siege gun, while dismounted Federal cavalrymen stormed the walls of the fort.

    The men of the battery learned of the surrender of Lee's and Johnston's armies and the death of Lincoln on April 30, 1865, in Macon, Georgia. On May 24, the battery left Macon for home. They traveled through Atlanta and Chattanooga to Nashville. There they turned in their equipment and horses, and left for Indianapolis where they arrived on June 23, 1865. They were paid and discharged on June 30. According to one of the members, the battery had marched over 6,070 miles and traveled an additional 900 miles by rail during their three-year term of service. Of the 156 men who originally enlisted with the battery in 1862, only 77 were present when the battery was mustered out of service.