forty
thousand men; but General Pope ordered him, on the next morning, to
Manassas, where he hoped to "bag the whole crowd," he said--that is
to say, the force under Jackson. This was the fatal mistake made by
General Pope. Thoroughfare Gap was comparatively undefended. While
General Pope was marching to attack Jackson, who had disappeared, it
was the next thing to a certainty that General Lee would attack _him_.

All parties were thus moving to and fro; but the Confederates enjoyed
the very great advantage over General Pope of knowing precisely
how affairs stood, and of having determined upon their own plan of
operations. Jackson, with his back to the mountain, was waiting for
Lee. Lee was approaching rapidly, to unite the two halves of his army.
General Pope, meanwhile, was marching and countermarching, apparently
ignorant of the whereabouts of Jackson,[1]

General Lee, in personal command of Longstreet's corps, reached the
western end of Thoroughfare Gap about sunset, on the 28th, and the
sound of artillery from the direction of Groveton indicated that
Jackson and General Pope had come in collision. Jackson had himself
brought on this engagement by attacking the flank of one of General
Pope's various columns, as it marched across his front, over the
Warrenton road, and this was the origin of the sound wafted to General
Lee's ears as he came in sight of Thoroughfare. It was certainly
calculated to excite his nerves if they were capable of being excited.
Jackson was evidently engaged, and the disproportion between his
forces and those of General Pope rendered such an engagement extremely
critical. Lee accordingly pressed forward, reached the Gap, and the
advance force suddenly halted: the Gap was defended. The Federal force
posted here, at the eastern opening of the Gap, was small, and wholly
inadequate for the purpose; but this was as yet unknown to General
Lee. His anxiety under these circumstances must have been great.
Jackson might be crushed before his arrival. He rode up to the
summit of the commanding hill which rises just west of the Gap, and
dismounting directed his field-glass toward the shaggy defile in
front.

[Footnote 1: "Not knowing at the time where was the enemy."--_General
Porter_.] and undecided what course to pursue.

[Illustration: Lee Reconnoitring at Throughfare Gap.]

The writer of these pages chanced to be near the Confederate commander
at this moment, and was vividly impressed by the air