Lee lost no time. His first move was to get Pope's advanced troops defeated by Jackson, who brought more than double numbers against Banks at Cedar Run on the ninth of August. The Federals fought magnificently, nine against twenty thousand men. After the battle Jackson marched across the Rapidan, and Halleck wisely forbade Pope from following him, even though the first of Burnside's men (now the advanced guard of McClellan's army) had arrived at Aquia and were marching overland to Pope. Then followed some anxious days at Federal Headquarters. Jackson vanished; and Pope's cavalry, numerous as it was, wore itself out trying to find the clue. McClellan was still busy moving his men from Harrison's Landing to Fortress Monroe, whence detachments kept sailing to Aquia. What would Lee do now? On the thirteenth he began entraining Longstreet's troops for Gordonsville. On the fifteenth he conferred with his generals. And on the seventeenth, from the lookout on Clark's Mountain, he saw Pope's unsuspecting army camped round Slaughter Mountain within fifteen miles of the united Confederates. Halleck had just given Pope the fatal order to "fight like the devil" till McClellan came up. Pope was full of confidence. And there he lay, in a bad strategic and worse tactical position, and with slightly inferior numbers, just within reach of Jackson and Lee. Pope was, however, saved from immediate disaster by an oversight on the part of Stuart. In ordering Fitzhugh Lee's cavalry brigade to rendezvous at Verdierville that night Stuart forgot to make the order urgent and the missing brigade came in late. Stuart, anxious to see the enemy's position for himself, rode out and was nearly taken prisoner. His dispatch-box fell into Pope's hands, with a memorandum of Jackson's reinforcements. Jackson was for attacking next day in any case and groaned aloud when Lee decided not to, owing to the failure of cavalry combination in front and the belated supplies in the rear. Pope retired safely on the eighteenth, and on the nineteenth a thick haze hid his rear from Lee's lookout.