The following post first appeared on the blog of Antietam Battlefield Guide Jim Rosebrock (South From the North Woods) on Nov. 18, 2012.
This year, Savas Beatie published Volume II of Ezra Carmen’s monumental manuscript under the outstanding editorial pen of Tom Clemens. Tom’s work combines the manuscript of Carmen with the Copes maps for the best primary source account of this decisive battle. The most exceptional aspect of this book is Tom’s brilliant footnotes and references. He goes beyond merely citing a reference and includes a full degree of careful analysis. Here is an example.
Much is made (generally negative) of McClellan’s concentration of his cavalry, behind the center of his line.
In Landscape Turned Red, Stephen Sears has this to say: Shortly before noon, McClellan had ventured to push several batteries across the Middle Bridge, supported by Pleasonton’s cavalry and a force of regulars from George Syke’s Fifth Corps. He was nervous about the move-it was taken against the advice of Porter and Sykes-and he cautioned Pleasonton not to risk the batteries unduly. As an afterthought, he asked, “Can you do any good by a cavalry charge?” Pleasonton wisely ignored the suggestion.
There is also a quotation in Carmen’s manuscript that criticizes the concentration of the cavalry in the center: “Another, a gallant young cavalry officer later in the war, says: ‘It is one of the surprising features of this surprising battle that the Federal cavalry, instead of being posted, according to the practice of the centuries, on the flanks of the infantry, was used throughout the day in support of its horse batteries, in rear of he Federal center, and in a position from which it could have been impossible for it to have been uses ad cavalry, or even to have emerged mounted.’”
In Tom Clemen’s footnote to this quotation, we learn that the “gallant young cavalry officer” is George B. Davis. But Tom goes beyond identifying the author of this quote to take on the issue of the doctrinal soundness of Pleasonton’s cavalry position. Here is the complete cite: George B. Davis, The Antietam Campaign, in Campaigns in Virginia, Maryland and Pennsylvania 1862-1863, vol. 3, Papers of the Military Historical Association of Massachusetts (Boston, MA: Griffith-Stillings Press, 1903), p. 55. Davis had worked on publishing the Official Records and was the chair of the Antietam Battlefield Board, Susan Trail, Remembering Antietam, unpublished doctoral dissertation, Antietam National Battlefield Library. Davis’ opinion though worthy of respect, may be challenged by the strategic manual used as a textbook at the U.S. Military Academy in the antebellum era. Baron De Jomini, Summary on the Art of War, or a New Analytical Compend of the Principal Combinations of Strategy, Grand Strategy and Military Policy (New York, NY: G.P. Putnam & Co., 1854, pp 305-309, discussed cavalry placement and use in various situations, including a charge upon broken infantry lines with artillery support making success possible, and cited examples to demonstrate it. McClellan’s placement was consistent with Jomini’s principals.” (My bold)
Tom makes a very important point here. Jomini was studied at West Point and his book states that this is a legitimate use of cavalry. McClellan’s employment was just as doctrinally sound in the constructs of the time as Lee’s was. Lee follows the more generally known employment of cavalry placing Fitzhugh Lee’s brigade and Pelham’s artillery are on the left flank, Thomas Munford’s brigade on the right, and Wade Hamptons brigade in reserve in the center. But as Jomini makes plain, that is by no means the only possible course of action. Sadly, many don’t reach this point.
The conventional interpreters ignore or are unaware of this fact. Sears says that Pleasonton “wisely ignored” McClellan’s suggestion. George Davis sets in stone the idea that cavalry is only employed on the flanks on the battlefield “according to the practice of the centuries”.
Some will argue that his failure to place the cavalry on the flanks prevented him from detecting the advance of A.P. Hill’s division. The reality is that the Union signal station on Red Hill had the Federal left flank of the battlefield under constant observation and detected the advance of Hill’s division. Some will proclaim McClellan’s failure to place cavalry on the flanks as an oversight or a mistake. McClellan is acknowledged, even by his most virulent detractors to be to careful and methodical planner to have overlooked the flanks. His move is a conscious decision to concentrate in the center.
I would go so far to venture this possibility. McClellan has poised his cavalry for an offensive move. The Middle Bridge corridor and Boonsboro Pike is the shortest and fastest route to the Potomac River. It is a risky venture and one that goes against the grain of the typical McClellan portrayal as a conservative commander. Consider that this is the first time that McClellan has concentrated his cavalry into one combat command. It is still a relatively weak vessel compared to the mighty legions of JEB Stuart’s cavalry division. Alfred Pleasonton, a decidedly mixed bag in terms of competence, commands the division. But the move is in the right direction. Not only is the cavalry division concentrated but it has also advanced across the Antietam and is poised further offensive action. The use or potential use of cavalry as an offensive weapon is a first in the annals of the Army of the Potomac. My point today is only to assert the legitimacy and doctrinal soundness of the employment. McClellan’s actual use of the cavalry later that afternoon is another matter that can be discussed at another time.
For those who would say that the placement of mobile forces in the center for a decisive attack there is doctrinally unwise and never works need only ask the French Army in 1940. That was their assumption until Guderian’s XIX Panzer Corps crossed the Meuse at Sedan and broke the French center.
So lets take off the table the idea that McClellan’s concept for deploying the cavalry was NOT doctrinally sound.
 Sears, Stephen, Landscape Turned Red The Battle of Antietam, New York: Ticknor and Fields, 1983. page 271.
 Carmen, Ezra. The Maryland Campaign of 1862 Volume II Antietam, edited by Tom Clemens, El Dorado CA: Savas-Beatie, 2012, page 364.