Antietam’s Lower Field Revisited Part II: The Unsteady Ninth Corps at Antietam

The Ninth Corps had an odd relationship with the Army of the Potomac during the Civil War. Mirroring their involvement with the army was that of their best-known commander, Ambrose Burnside, who would eventually command the army, then serve with it later in 1864.

The corps was a newcomer to the army in 1862, part of it having joined it in time to fight at Second Manassas. The entire corps of four divisions then joined in the pursuit across Maryland just a week before the battle at Antietam.

The Ninth Corps in 1862 included the Kanawha Division, composed of six Ohio regiments who would be transferred away after this campaign. Antietam was their only major battle and only one with the Army of the Potomac. Thus the Ninth Corps and its units do not have a long or storied association with the army as did the First, Second, Fifth, or Sixth Corps. Even its corps badge is different: rather than a simple shape like the others, it features a shield with a crossed cannon and anchor, reflecting their participation in amphibious operations in North Carolina early in the war.

These Ninth Corps troops had different origins: some had begun the war in western Virginia (now West Virginia), others on the North Carolina coast. They then were transferred to service in Virginia. At Newport News in July 1862, three divisions were joined and established as the Ninth Corps. Later the Kanawha Division joined the formation. Its long-time famous commander, General Ambrose E. Burnside, gained a poor command reputation at Antietam, Fredericksburg, and the Crater at Petersburg.

After Fredericksburg these troops were transferred west, fighting at Vicksburg and Knoxville, then back to Virginia for the 1864 Overland Campaign. They were the only corps to fight in the east with the Army of the Potomac, move to the western theater, then return to Virginia. Yet in this return to the eastern theater they were not officially part of this army, just working with it, as Burnside’s commission superseded army commander George Meade’s.  (this resulted in a delicate and complicated command problem, as Meade oversaw the Army of the Potomac and had to work with Burnside, who got his orders directly from General in Chief U.S. Grant).

There was little time for these separate commands to work together or form a sense of identity, crucial for entering combat at Antietam. The corps had another challenge: many of its units were brand new or had very limited combat experience. Some fought for the first time or had only fought in one major battle- Second Manassas or South Mountain. Antietam would be the first battle for the 100^th Pennsylvania, 16^th Connecticut, 17^th Michigan, 35^th Massachusetts, and 9^th New Hampshire.  Several others, including the 30^th Ohio and 103^rd New York had seen some combat but were hardly seasoned veterans.  They were as green as the rookie units. As at the brigade and division command level, there was little chance for units or commanders to build working relationships.

In addition, the Union Ninth Corps never did quite fit in with the Army of the Potomac.  Elements of the corps joined the army in time for Second Manassas, but the other corps of the army had served together in the Peninsula then the Seven Days’ Campaigns. There they established their reputations and created their own culture. The Ninth Corps was not part of that shared experience, nor did it participate in the army’s greatest victory, Gettysburg.

Lastly, the corps had an awkward command structure as a result of army commander George B. McClellan suddenly scrapping his wing system. McClellan created two wings for the Army of the Potomac on September 14, and the next day the system was abruptly abandoned. McClellan never made it clear why he implemented the wing system, or what he expected of it, or why he suddenly abandoned it on the eve of battle.

General Edwin V. Sumner led one wing, composed of his Second and the Twelfth Corps, General Burnside led the other, consisting of the First Corps and his own Ninth. With Burnside’s elevation, General Jesse Reno assumed corps command, yet Reno was killed at South Mountain. Then General Jacob D. Cox assumed corps command. Cox noted that upon returning from a meeting with McClellan on the evening of the 16^th Burnside was “disturbed and grieved at the course things had taken” with the break up of his wing. Not a good mindset for a commander who would be expected to play a major role in a coming battle.

McClellan did not offer either an explanation, or advice on how to proceed. It created the awkward situation of Burnside now reverting to corps command, or at least commanding only once corps, as the First Corps ended up on the other side of the battlefield from the Ninth. McClellan’s’ orders came to Burnside and he passed them on to Cox. Burnside and Cox would have to develop a way to handle the corps, and in this they largely failed.

Thus Burnside received orders from army headquarters, and passed them on to Cox to implement. Could Burnside have inquired of McClellan how to proceed? Could McClellan have clarified the situation and what he expected? Could Cox or Burnside have tried to decide between them how to handle the situation? Did it make Cox cautions in not wanting to act aggressively and appear to undercut Burnside? These are lingering questions that must be recognized in our analysis of Antietam.

Regardless, the Ninth Corps at Antietam is a unique case study of one particular corps at a moment in time. Recently joining the army, composed of newly formed divisions, with many raw regiments, it was tasked with fighting alone, crossing a major obstacle in the creek, and occupying an area too large for its numbers.

The author thanks Kevin Pawlak for his advice and input.