The capture of Manassas, to use Pope’s own words, rendered his position at Warrenton no longer tenable, and early on the 27th, the army, instead of concentrating on Warrenton, was ordered to move to Gainesville (from Gainesville it was easy to block Thoroughfare Gap); Buford’s cavalry brigade was thrown out towards White Plains to observe Longstreet, and Hooker was dispatched to clear up the situation at Manassas.  This move, which was completed before nightfall, could hardly have been improved upon.  The whole Federal army was now established on the direct line of communication between Jackson and Lee, and although Jackson might still escape, the Confederates had as yet gained no advantage beyond the destruction of Pope’s supplies.  It seemed impossible that the two wings could combine east of the Bull Run Mountains.  But on the evening of the 27th, after the conclusion of the engagement at Bristoe Station, Pope lost his head.  The view he now took of the situation was absolutely erroneous.  Ewell’s retreat before Hooker he interpreted as an easy victory, which fully compensated for the loss of his magazines.  He imagined that Jackson had been surprised, and that no other course was open to him than to take refuge in the intrenchments of Manassas Junction and await Lee’s arrival.  Orders were at once issued for a manoeuvre which should ensure the defeat of the presumptuous foe.  The Federal army corps, marching in three columns, were called up to Manassas, a movement which would leave Thoroughfare Gap unguarded save by Buford’s cavalry.  Some were to move at midnight, others “at the very earliest blush of dawn.”  “We shall bag the whole crowd, if they are prompt and expeditious,"* (* O.R. volume 12 part 2 page 72.) said Pope, with a sad lapse from the poetical phraseology he had just employed.

August 28.

And so, on the morning of the 28th, a Federal army once more set out with the expectation of surrounding Jackson, to find once more that the task was beyond their powers.

The march was slow.  Pope made no movement from Bristoe Station until Hooker had been reinforced by Kearney and Reno; McDowell, before he turned east from Gainesville, was delayed by Sigel’s trains, which crossed his line of march, and it was not till noon that Hooker’s advanced guard halted amid the still smouldering ruins on the Manassas plateau.  The march had been undisturbed.  The redoubts were untenanted.  The woods to the north were silent.  A few grey-coated vedettes watched the operations from far-distant ridges; a few stragglers, overcome perhaps by their Gargantuan meal of the previous evening, were picked up in the copses, but Jackson’s divisions had vanished from the earth.