Centreville.
During the afternoon Longstreet, throwing a brigade across Bull Run
to keep the enemy on the qui vive, followed the same route. Of these
movements Pope received no warning, and Jackson's proclivity for
flank manoeuvres had evidently made no impression on him, for, in
blissful unconsciousness that his line of retreat was already
threatened, he ordered all waggons to be unloaded at Centreville, and
to return to Fairfax Station for forage and rations.

September 1.

But on the morning of September 1, although his whole army, including
Banks, was closely concentrated behind strong intrenchments, Pope had
conceived a suspicion that he would find it difficult to fulfil his
promise to Halleck that "he would hold on." The previous night Stuart
had been active towards his right and rear, capturing his
reconnoitring parties, and shelling his trains. Before noon suspicion
became certainty. Either stragglers or the country people reported
that Jackson was moving down the Little River turnpike, and
Centreville was at once evacuated, the troops marching to a new
position round Fairfax Court House.

Jackson, meanwhile, covered by the cavalry, was advancing to
Chantilly--a fine old mansion which the Federals had gutted--with the
intention of seizing a position whence he could command the road. The
day was sombre, and a tempest was gathering in the mountains. Late in
the afternoon, Stuart's patrols near Ox Hill were driven in by
hostile infantry, the thick woods preventing the scouts from
ascertaining the strength or dispositions of the Federal force.
Jackson at once ordered two brigades of Hill's to feel the enemy. The
remainder of the Light Division took ground to the right, followed by
Lawton; Starke's division held the turnpike, and Stuart was sent
towards Fairfax Court House to ascertain whether the Federal main
body was retreating or advancing.

Reno, who had been ordered to protect Pope's flank, came briskly
forward, and Hill's advanced guard was soon brought to a standstill.
Three fresh brigades were rapidly deployed; as the enemy pressed the
attack a fourth was sent in, and the Northerners fell back with the
loss of a general and many men. Lawton's first line became engaged at
the same time, and Reno, now reinforced by Kearney, made a vigorous
effort to hold the Confederates in check. Hays' brigade of Lawton's
division, commanded by an inexperienced officer, was caught while
"clubbed" during a change of form