But this was not the intention of the enemy; for on the 3d he had disappeared from the front of Washington
, and the information received of his movements induced the belief that he intended to cross the Upper Potomac
This made an active campaign necessary in order to cover Baltimore
, prevent the invasion of Pennsylvania
, and clear Maryland
; and measures were immediately taken accordingly.
was left in command of the defences of Washington
; and on the 4th of September a forward movement of the army was commenced, and General McClellan
himself left the capital and took the field on the 7th.
At this time it was known that the mass of the rebel army had passed up the south side of the Potomac
, in the direction of Leesburg
, and that a portion had crossed into Maryland
; but whether they intended to send over their whole force with a view to turn Washington
by a flank movement down the north bank of the Potomac
, or to move on Baltimore
, or to invade Pennsylvania
, were matters of uncertainty.
This constrained General McClellan
to proceed with great caution for a few days, and so move as to keep both Baltimore
covered, and at the same time hold the troops in readiness to follow the enemy if he went into Pennsylvania
The general course of the march was in a northwesterly direction, the points of destination being the city of Frederick
, and its vicinity.