Hooker was out of ammunition. Pope ordered Porter to join him, but he did not obey the order. Jackson was in a dangerous place. He was not strong enough to advance and give battle to Pope, who was now pressing him. He must retreat and gain time,--delay an engagement till Lee could come up. He fell back before Pope from Manassas to Centreville, then turned west over the Warrenton turnpike, along which McDowell's army marched in the first battle of Bull Run, the 21st of July, 1861. At this moment McDowell was moving east on the same turnpike. At six o'clock King's division of McDowell's corps, which was in advance, came in collision with Jackson at Groveton, on the western edge of the old battle-field. Gibbon's and Doubleday's brigades were engaged a short time, but darkness put an end to the conflict. Pope, with Hooker, Kearny, and Reno, had reached Centreville; Porter was at Manassas Junction; Banks, south of it; while Sigel and McDowell were southwest of Jackson, towards Warrenton. Jackson was in danger of being crushed. Pope, instead of being ground to powder, had maneuvered so admirably that he felt almost sure that Jackson would be utterly routed. He lost no time in sending out orders. "Hold your ground at all hazards," was his despatch to General King. "Push on at one o'clock to-night," was the word sent to Kearny, who was to move west over Warrenton turnpike and attack Jackson's rear. "Assault vigorously at daylight," he added, "for Hooker and Reno will be on hand to help you." "Move on Centreville at the earliest dawn," was the order sent to Porter at Manassas. General Pope was sure that he could crumble Jackson before Longstreet, who, he knew, was rapidly advancing towards Thoroughfare Gap, could arrive. Ricketts's division was thrown north, to hold the gap. But General King's troops were exhausted. Instead of holding the ground, he fell back towards the junction. General Ricketts sent a small force up to the gap, but Longstreet, who had reached Salem, sent a part of his troops over the mountains north, gained their rear, forced them back, and thus opened the gate for the advance of his corps. Ricketts joined McDowell at the junction. All this made it necessary for General Pope to issue new orders. He sent out his aides. "Attack at once," was the word to Sigel. "Push down the turnpike, as soon as possible, towards any heavy firing you may hear," was the despatch to Kearny and Hooker, also to Reno, commanding a division of Burnside's corps. "Be on the field at daybreak," was the message to Porter. "Send your train to Manassas and Centreville. Repair the railroad to Bull Run. Work night and day," were the instructions to Banks, who was guarding the trains. It was of the utmost importance that the attack should be made instantly, before Longstreet arrived; and to that end General Pope directed all his energies. CHAPTER X. BATTLE OF GROVETON.