At the same time it was his intention to have Slocum follow up Lee's advance, by keeping in his rear, to capture his trains and couriers, and to cut off his retreat should he be defeated.
General Meade's first order was for all the troops to concentrate in Frederick, where he proposed to have a grand review; but at the urgent remonstrance of General Butterfield, who had been Hooker's Chief of Staff, and who stated that this delay would give Lee time to cross the Susquehanna, and capture Harrisburg and Philadelphia, Hooker's orders were allowed to stand, with some exceptions.

Meade appears to have disapproved all movements against Lee's line of retreat, for he ordered Slocum to rejoin the main army, and had the hardihood to break up the post at Harper's Ferry, in spite of the fact that Hooker had just been relieved from command for requesting permission to do so.

The bulk of the garrison, under Major-General French, was directed to take post as a reserve at Frederick, when our forces moved forward.

The general idea of our advance was to interpose between the enemy and Philadelphia if he went north, or between him and Baltimore and Washington in case he turned back.

The orders at night were for Buford's division of cavalry to take post on the left flank, in the direction of Fairfield; Gregg's division on the right flank at Westminster; and Kilpatrick's division in advance of the centre, at Littlestown, the different corps to be posted between New Windsor and Emmetsburg.
Ewell's corps, as stated, were at Carlisle and York, Lee and Longstreet's at Chambersburg, and Hill's corps at Fayetteville.
Lee was startled to learn from a countryman who came in on the 28th that Hooker was at Frederick, and not south of the Potomac, as he had supposed.