The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 2: Two Years of Grim War.
Francis Trevelyan Miller, Ed.

The amazement at the North when the news of the capture of Manassas became known cannot be described. But the newspapers belittled it, declaring that it was merely a bold raid and that for any large force to get between Pope's army and Washington before Pope became aware of the attempt was simply impossible.

Jackson had done an astonishing thing. But his position was precarious, nevertheless. Pope was moving toward him with a far larger army, recently augmented by Heintzelman's corps from the Army of the Potomac, while Fitz John Porter with an additional force was not far off. It is true that Longstreet was hastening to the aid of Jackson, but he had to come by the same route which had brought Jackson — through Thoroughfare Gap — and Pope thought he saw a great opportunity. If he could only detain Longstreet at the gap, why should he not crush Jackson with his superior numbers? To this end he sent orders to Porter, to McDowell, and to Kearny and others whose forces were scattered about the country, to concentrate during the night of the 27th and move upon Jackson. McDowell sent Ricketts with a small force — too small — to prevent Longstreet from passing through Thoroughfare Gap, and hastened to join the main army against Jackson. But that able commander was not to be caught in a trap. He moved from Manassas Junction by three roads toward the old battle-field of Bull Run and by noon on the 28th the whole corps was once more united between Centreville and Sudley Spring. Late in the day he encountered King's division of McDowell's corps near the village of Groveton, and a sharp fight was opened and kept up till an hour after dark. The Confederates were left in possession of the field.

The following day, August 29th, was the first of the two days battle, leaving out of account the fight of the evening