alternatehistory.com

28 June

J.E.B. Stuart sets off from Leesville. In order to fool any Union spies, the formation had been undergoing preparations for a strategic move west - Stuart did not know his own instructions until he opened them yesterday. Fortunately, as the move was to involve travel off the railroads, the Cavalry Division is well prepared for their planned operations - a move north to threaten McClellan's eastern flank.

The Cavalry Division crosses the Potomac at Point of Rocks at 10:30 AM. Riding at a fast trot (possible because there are very few Union infantry in the way) they pass through Frederick and continue north. At one point Stuart encounters a (depleted) Federal regiment, which delays him for half an hour before he can set up a rifle base of fire and charge home with the rest (causing him about two hundred casualties counting wounded, but scattering the Federal regiment and causing them to flee north).
The news flashes ahead of Stuart on the telegraph, reaching McClellan around 1 PM - whose first response is shock, then relief he has not expended his reserve, then a kind of fatalism as he begins planning how he will react.
The first priority is to send his reserve north to Chambersburg - the loss of his supply depot would inevitably lead to the loss of the whole army, and McClellan considers preventing this unmitigated disaster to be a matter of overriding importance. Once this is done, however, he will need to disengage his entire army and send it north - five thousand (ten thousand? Fifteen?) Confederate cavalry on his line of communication, cutting the railroad from Pittsburgh (his only remaining rail supply line) and all the good roads would be almost as big a problem, and to keep his supply lines open he needs to relocate to where he can operate against Confederate attackers.

By 3 PM, the reserve division is marching north. McClellan hopes they can reach Chambersburg while there is still daylight, though worries about the ability of tired troops to defend the supply depot, and turns his attention to the matter of moving the rest of the army.
Before his plans are well advanced, however, Lee begins an attack - his rifles working forwards to deliver covering fire, and a division under Holmes launching an assault with the bayonet. They are turned back, the volleys of that wing of the Army of the Potomac sufficing to prevent the assaulting division from reaching their goal, but McClellan finds himself with a difficult problem indeed to solve - if he pulls out, Lee will pursue him closely, and only by abandoning his artillery can he move too fast to pursue (but replacement artillery is simply not available) whereas if he holds in position then the cavalry force (already seeming to loom larger and larger in his assessments, as scattered reports come in of the Confederate cavalry overwhelming all before them - mainly because most of the troops which should be in their way are in the embrasures here, in reality) will cut him off and force his surrender.

As such, McClellan makes the difficult decision to leave a rearguard. He has the drovers (who are not armed, as he has insufficient rifles or muskets) help to set up hasty fallback positions, and at 5 PM issues a series of orders - the upshot of which is that the wings under McDowell and Keyes will march north, followed by Heintzelman's III Corps, and that Sumner's II Corps will cover their retreat.

There is logistical chaos, and McClellan decides to leave the execution of his orders to the following day - attempting to pull out of defensive positions and march by night seems to be asking for trouble.


The reserve division reaches Chambersburg as the sun goes down, and Porter (in charge of the reserves) belatedly realizes that the real danger is further north still, in Carlisle - the northern end of this section of the valley. He sends riders back to McClellan and continues marching north, his force diminished by a brigade left in Chambersburg to protect the supply depot.

Things in the Valley are quickly falling under the fog-of-war, with nobody (including Stuart) entirely sure what all the parts of their armies are doing. One thing that is clear, however, is that the campaign has taken on something of the character of a race towards Harrisburg.