...sition assigned him on Ewell's right; but at the critical moment Hooker's movement toward the Potomac began, and delayed Stuart's crossing of the river two days. Thus it occurred that when he entered Maryland on the night of the 27th, the whole of the Federal army was also in Maryland, and communication with General Lee was cut off; for, as Mosby says, Pleasanton's cavalry, which was the rear guard of th...