Sigel attacked the enemy about daylight on the morning of the 29th, a mile or two east of Groveton, where he was soon joined by the divisions of Hooker and Kearny. Jackson fell back several miles, but was so closely pressed by these forces that he was compelled to make a stand and to make the best defense possible. He accordingly took up a position with his left in the neighborhood of Sudley Springs, his right a little to the south of Warrenton turnpike, and his line covered by an old railroad grade which leads from Gainesville in the direction of Leesburg. His batteries, which were numerous, and some of them of heavy caliber, were posted behind the ridges in the open ground on both sides of Warrenton turnpike, whilst the mass of his troops was sheltered in dense woods behind the railroad embankment.

I arrived on the field from Centreville about noon, and found the two armies confronting each other, both considerably cut up by the sharp action in which they had been engaged since daylight in the morning. Heintzelman's corps occupied the right of our line, in front or west of the Sudly Springs road. General Sigel was on his left, with his line extended a short distance south of the Warrenton turnpike, the division of General Schenck occupying the high ground to the left of that road. The extreme left was occupied by the division of General Reynolds. General Reno's corps had reached the field, and most of it had been pushed forward into action, leaving four regiments in reserve and in rear of the center of our line. Immediately after I reached the ground General Sigel reported to me that his line was weak; that the divisions of Schurz and Steinwehr were much cut up, and ought to be drawn back from the front. I informed General Sigel that this was utterly impossible, as there were no troops to replace them, and that he must hold his ground; that I would not again push his troops into action, as the corps of Porter and McDowell were moving forward from Manassas Junction on the road to Gainesville and must very soon be in position to fall upon the enemy's right flank and probably upon his rear. I rode to the front of our line and inspected it from right to left, giving the same information to Generals Heintzelman and ReNumbers The troops were accordingly suffered to rest in their positions and to resupply themselves with ammunition. From 12 o'clock until 4 very severe skirmishes occurred constantly at various points on our line, and were brought on at every indication that the enemy made of a disposition to retreat.

About 2 o'clock in the afternoon several pieces of artillery were discharged on the extreme right of the enemy's line, and I fully believed that Generals Porter and McDowell had reached their positions and had become engaged with the enemy. I did not hear more than three shots fired, and was at a loss to know what had become of these two corps or what was delaying them; but I received information shortly afterward that General McDowell was advancing to join the main body by the Sudly Springs road, and would probably be up with us in two hours. At 4.30 o'clock I sent a peremptory order to General Porter to push forward at once into action on the enemy's right, and, if possible, to turn his rear, stating to him generally the condition of things on the field in front of me. About 5.30 o'clock, when General Porter should have been coming into action in compliance with this order, I directed Generals Heintzelman and Reno to assault the left of the enemy. The attack was made with great gallantry, and the whole of the left of the enemy was doubled back toward his center, and our forces, after a sharp conflict of an hour and a half, occupied the field of battle, with the dead and wounded of the enemy in our hands. In this