We have been working our way through Timothy Reese's High-Water Mark: The 1862 Maryland Campaign in Strategic Perspective and have come to a chapter where Reese must defend the idea that a battle was fought at Crampton's Gap.
I never knew this was an issue until I moved to Maryland and discovered that there is a notion that holds only one battle was fought, called "South Mountain," and that this one fight is made up of parts. This idea holds sway over the state park service, unfortunately.
Unless they are accidents, battles are tactical manifestations of operational intent. If the operational intent for subordinate commands is different, the battles are different. It is simplistic to lump actions together because they are close in time or space.
Objectors to this formula might cite hierarchy of command, i.e. that Franklin was a subordinate; his operations were subordinate by definition. There are two answers to this. First, Reese has shown that Franklin's orders contained separate objectives and wide discretion. I would say those orders divided McClellan's army and raised Franklin to something like interim commander of the lesser part. Secondly, today's Army well understands that "The intended purpose, not the level of command, determines whether an Army unit functions at the operational level." Thus a corps can function at the army's (operational) level. This modern doctrinal statement embodies a philosophical truth that applies to all battles at all times. Franklin fought his own battle in a place apart with a unique purpose and wide discretion.
If Franklin, at Crampton's Gap, was operating at least on the operational level, which I suggest as a minimum threshold, then he was working one level higher than the commanders at Fox's and Turner's who served a simple, tactical end – forcing the passes. Reese argues that Franklin was also serving strategic goals – I agree with him. If he is correct, then Franklin was operating two levels above Burnside, Hooker and the others, and it is slovenly thinking to lump them all together.
Reese says: "Crampton's Gap was without question a fundamentally strategic operation, exclusively triggered by the Lost Order."
This last point is important. There would have been a battle of the gaps at Fox's and Turner's whether or not McClellan found the Lost Orders – they would have flowed from a meeting engagement and from Longstreet's orders. They would have happened about when they did due to the tempo of McClellan's advance prior to finding Lee's dispatch. McClellan's orders to Franklin, on the other hand, sought a battle to exploit the possibilities seen in Lee's dispersion.
I should let Reese speak:
Through size [of engagement] alone, precedence must be assigned in descending order of gaps north to south, Turner's, Fox's, and Crampton's. Measured in Federal tactical success, they would be prioritized Crampton's, Turner's, and then Fox's. Strategically speaking, however, Crampton's Gap again surpasses both northern gaps individually and collectively by merit of its impact on Lee's rapidly dwindling options. South Mountain froze the campaign initiative. Crampton's Gap wrenched it from Lee's grasp and conclusively closed his expedition into Maryland. […] Therefore Crampton's Gap and South Mountain were, and remain, two wholly separate though synchronous engagements, fought independently by autonomous wings of both armies for wholly distinct campaign objectives.
More on this new book Thursday.