On October 8th, Gen. Robert E. Lee ordered Maj. Gen. J.E.B. Stuart to take his cavalry on a raid into Maryland, and even as far as Chambersburg, Pennsylvania, to cut the Cumberland Valley Railroad supplying Maj. Gen. George B. McClellan's army at Haggerstown. Further, Stuart was to gather intelligence on Union numbers, supplies, and intentions. It was a typical cavalry operation, the sort of independent mission that Stuart loved.
On the 10th, Stuart led 1,800 troopers north from their Virginia camps toward the Potomac River. They rode to McCoy's Ford several miles above Harpers Ferry, sliced across the narrow Maryland panhandle, and rode into Pennsylvania that same day. Already, a Union pursuit was mounting.
By nightfall, the cavalry reached Chambersburg. The startled citizens surrendered the town, and Stuart commenced at once its capture and destruction. By dawn the next morning, he was ready to leave, his mission only partly fulfilled, for the railroad was still intact. Guessing that McClellan would have cut off a return by way of the upper Potomac, Stuart led his men east to Cashtown, then south to Emmitsburg, maryland, continuing past Frederick to recross the Potomac finally at White's Ferry. In effect, he had ridden completely around McClellan yet again. Only at the final river crossing did Union cavalrymen catch him in an ineffectual attempt to cut off escape.
Stuart had covered more than 100 miles in 2 days, destroyed some stores, captured more, and severely disorganized the Union cavalry for weeks to come. Against a better opponent, Stuart's Chambersburg Raid would not have been significant. Against McClellan, however, it made an already timid general even more fearful.