[492] movements, thinking that as he could not prevent him from crossing the Potomac, it was therefore better to wait to attack him until he had separated himself from his base of operations. In order to watch and thwart his movements he would have desired that Pleasonton, with his entire corps, had passed along the right bank of the Potomac, and that a column of fifteen thousand men, taken from the garrisons of Washington and Baltimore, might come to form a junction with him when, following Lee's march, he should have reached the eastern slope of South Mountain. The first project was not relished by the President; the second met with all kinds of obstacles, which we will explain hereafter.
The counter-order issued to the army, however, did not reach Pleasonton in time, as he had set off at daybreak for the purpose of clearing his march. He was already on his way to Aldie when ordered to come back. The country he was passing through was very rough, covered with woods, and consequently favorable to sudden attacks and any secret movements which the enemy might attempt: in front of him lay the range of high hills which Aldie Gap divides. Appreciating the importance of having the other slope reconnoitred, he asked and obtained permission to continue his march as far as the foot of the Blue Ridge: if he did not encounter the enemy, he was to push forward, by way of Leesburg, as far as the neighborhood of Harper's Ferry. Gregg's division was at the head, the Second brigade, under Kilpatrick, forming the advance. Three regiments of this brigade, followed very closely by a portion of the First, proceeded toward Aldie. Colonel Duffie, with the First Rhode Island, detached by Kilpatrick, had been at Thoroughfare Gap since morning, and was to join him at Middleburg.
On the same day, Stuart, after receiving some detailed information from Mosby regarding the positions which the Federals had occupied the day before, and believing them still far distant from the Bull Run Mountains, left his bivouacs along the Manassas Railroad to occupy the passes of these mountains. Chambliss, following the road which crosses Thoroughfare Gap, was ordered to post himself at Salem in order to watch this defile; Munford to pass through Middleburg and occupy Aldie; and Robertson to
