In one of these expeditions a locomotive and twenty-three cars were disabled on the Baltimore and Ohio Railroad.

Imboden, too, who occupied Cumberland on the 17th, in order to favor the general plan of invasion, tore up some miles of the track west of that town, with a view to prevent any reinforcements coming from that direction.
It would have been much better for the interests of the Southern Confederacy if Lee, instead of making a downright invasion, had been content to remain in the valley and threaten Hooker with two corps, while he used the third to procure unlimited supplies in Pennsylvania, and to sever all connection between the East and West, by breaking up the railroads and cutting the telegraph wires.
Such a result, however, would hardly have been sufficient to meet the expectations of the Southern people, who were bent upon nothing else than the entire subjugation of the North and the occupation of our principal cities.
Pleasonton's operations having cleared the way, Hooker moved forward promptly on the 18th to occupy the gaps.

The Twelfth Corps were sent to Leesburg, the Fifth to Aldie, and the Second to Thoroughfare Gap.

The other corps formed a second line in reserve.

This covered Washington and gave Hooker an excellent base of operations.
In answer to his demand for reinforcements, Crawford's division of Pennsylvania Reserves, and Abercrombie's division were sent to him.
As the latter was just going out of service, it was of no use.
Hooker contended that his army constituted the proper defence of Washington, and that it was not necessary to keep a large force inactive there, who could be of much more service at the front.
The authorities were timid, however, did not see the force of this reasoning and therefore refused to place Schenck's and Heintzelman's commands under his orders.
The enemy made a feeble attempt about this time to occupy Harper's Ferry, but were promptly shelled out by our batteries on Maryland Heights.
Lee having failed, on account of the discomfiture of his cavalry, in crossing the Potomac at Edwards' Ferry, was forced either to remain where he was or go forward.