IX Corps (Ninth Army Corps) was a corps of the Union Army during the American Civil War that distinguished itself in combat in multiple theaters: the Carolinas, Virginia, Kentucky, Tennessee, and Mississippi. Corps history Formation, Second Bull Run, and Antietam Although the official order designating its number was not issued until July 22, 1862, the IX Corps organization dates from the expedition to North Carolina in February, 1862, under Ambrose E. Burnside and to the operations about Hilton Head, South Carolina, because the troops engaged in these movements were the only ones used in the formation of the corps. The corps was assembled by Burnside at Newport News, Virginia, from his two brigades from North Carolina and Isaac Stevens's division from Hilton Head. The corps consisted of three divisions, under Generals Stevens, Jesse L. Reno, and John G. Parke. After a short stay at Newport News the corps was ordered to reinforce Maj. Gen. John Pope's Army of Virginia, and at Second Bull Run it fought its first battle as the IX Corps. Only the two divisions of Stevens and Reno were engaged in this action; they numbered 12 regiments and 2 batteries, fewer than 5,000 men. General Reno was in command of both divisions in Burnside's absence. The losses in this small engagement amounted to 204 killed, 1,000 wounded, and 319 missing; total, 1,523. Some of the regiments encountered a severe fire, the 28th Massachusetts losing 234 men. General Stevens was killed at Chantilly. General Reno retained command of the corps on the Maryland Campaign, General Burnside having charge of the right wing of the Army of the Potomac, which was composed of the I and IX Corps. Brig. Gen. Orlando B. Willcox was appointed to the command of Stevens's (1st) Division, while the 2nd and 3rd Divisions were commanded, respectively, by Generals Samuel D. Sturgis and Isaac P. Rodman. During this campaign Jacob D. Cox's Kanawha Division from western Virginia was temporarily attached to the corps. The command had also been greatly strengthened by the accession of several new regiments, just organized under the recent call for troops, and its four divisions now numbered 29 regiments and 5 batteries, with 13,819 present for duty, including non-combatants. The Battle of South Mountain was fought wholly by Burnside's two corps, the IX Corps losing 157 killed, 691 wounded, and 41 missing; total, 889. The loss in the I Corps was