In the early hours of the morning the hills echoed with the firing of artillery, with which the day was opened. Porter made an infantry attack in the forenoon, but was met by the enemy in vastly superior numbers and was soon pressed back in great confusion. As the hours passed one fearful attack followed another, each side in turn pressing forward and again receding. In the afternoon a large part of the Union army made a desperate onslaught on the Confederate left under Jackson. Here for some time the slaughter of men was fearful. It was nearing sunset. Jackson saw that his lines were wavering. He called for reënforcements which did not come and it seemed as if the Federals were about to win a signal victory. But this was not to be. Far away on a little hill at the Confederate right Longstreet placed four batteries in such a position that he could enfilade the Federal columns. Quickly he trained his cannon on the Federal lines that were hammering away at Jackson, and opened fire. Ghastly gaps were soon cut in the Federal ranks and they fell back. But they re-formed and came again and still again, each time only to be mercilessly cut down by Longstreet's artillery. At length Longstreet's whole line rushed forward, and with the coming of darkness, the whole Union front began to waver. General Lee, seeing this, ordered the Confederates in all parts of the field to advance. With wild, triumphant yells they did so. It was now dark and there was little more fighting; but Lee captured several thousand prisoners. Pope retreated across Bull Run with the remnant of his army and by morning was ensconced behind the field-works at Centreville. There was no mistaking the fact that General Pope had lost the battle and the campaign. He decided to lead his army back to the entrenchments of Washington. After spending a day behind the embankments at Centreville, the retreat was begun. Lee's troops with Jackson in the advance pursued and struck a portion of the retreating army at Chantilly.