Cavalry Deployments at Antietam

Lately my thoughts have turned to the cavalry, and especially the cavalry under McClellan. I got to wondering a few things and so have read parts of all the regimental histories to check what regiments did at Antietam. A starkly different picture emerges. In the following I'll mark links to regimental histories, but I bookmarked the book, not the page.

At Antietam the apparent organisation of the cavalry is:

Centre (Pleasonton's group)

5th US Cavalry

2nd Brigade (Col. Farnsworth): 8^th Illinois (ref), 3^rd Indiana (ref), 1^st Massachusetts (ref) and 8^th Pennsylvania Cavalry (no ref found for 8th PA)

3rd Brigade (Col. Rush): 4th and 6th Pennsylvania Cavalry (no refs found, but Pleasonton's report puts them here)

4x Horse Batteries

Right Flank (attached to 1st Corps)

4^th Brigade (Col. McReynolds): 1^st New York (ref), 12^th Pennsylvania Cavalry (ref)

5^th Brigade (Col. Davis): 3^rd Pennsylvania (ref) and 8^th New York Cavalry(ref) (note, both histories agree they were on the right flank with Hooker, which is contradicted by Pleasonton's report, but supported by Hooker's report)*

15^th Pennsylvania Cavalry (det, 200 men at most) (ref)

2^nd New York Cavalry (2 sqns) (no ref, but was 1st Corps escort unit)

Left Flank (attached to 9th Corps)

6th New York Cavalry (ref)

The 6th US Cavalry was not on the field at any point during the 16th-18th, being in the Pleasant Valley attached to 6th Corps (ref)

In summary there were 14 major cavalry units on the field (excluding escort squadrons etc.). 7 were with Pleasonton, 6 were with Hooker and screened his advance. Only one was with on the left flank, the 6th New York Cavalry (only 4 sqns, one was detached as an escort). The opening shots of the battle were fired on the 16th by the 3rd squadron of the 3rd Pennsylvania Cavalry skirmishing in front of Hooker's Corps.

The history of the 6th NY is enlightening about the Battle of Antietam. They state that they did cross the Antietam and skirmished with Munford's brigade of cavalry, taking a few prisoners. Carman's map seems to place Whitting's regular cavalry brigade there too.

There is a lot of ambiguity here. No-one has done much research into the cavalry operations in this campaign, I suspect because even a casual inspection of the histories shows that the Federal cavalry totally dominated the Confederate cavalry on the field and this doesn't fit in with the required storyline (see Wittenberg for the current consensus). A lot more work needs doing, especially to find out what half of McClellan's cavalry were up to on the far right flank.

* Incidently, the 8th NY Cavalry was the only escapee unit from Harper's Ferry on the field.The 12th Illinois, 7th RI Sqn and 1st Md Sqn seem to have joined the army after the 17th.

PS: Many of the regimental histories describe the operations of the 14th-21st September 1862 as a single continuous fight. These continuous battles can be named by their conventions:

14th: Battle of South Mountain

15th: Battle of Boonsboro

16th: Battle of Sharpsburg Turnpike

16th-18th: Battle of Antietam

19th: Battle of Botoler's Ford

20th: Battle of Shephardstown

21st: Battle of Williamsport