No. 46. Report of. Colonel O. B. Willcox, First Michigan Infantry, commanding Second Brigade, Third Division.

DETROIT, MICH., September 3, 1862.

GENERAL: My brigade, the Second, of Heintzelman's division, marching in rear of Franklin's brigade, arrived at the Sudley Ford at about 12.30 p.m., July 21, 1861. The brigade now consisted of the First Michigan, Eleventh New York (Firew Zouaves), Thirty-eighth New York, and Arnold's battery. The Fourth Michigan had been left at Fairfax Station and Fairfax Court-House by the order of General McDowell. Halting for rest and water, I obeyed the general's orders to post Arnold's battery on a hill commanding the ford, with the First Michigan for support, and at 1 o'clock pushed forward with my two remaining regiments up the Sudley and Brentsville road. We marched about two miles, and came upon the left of what I supposed to have been Franklin's line, near the junction of the Warrenton and Sudley roads. The troops on our left were engaged in a desultory fire with the enemy, posted in the thicket and ravine across the Warrenton road, not far from the Robinson house. The Thirty-eighth New York was quickly formed in order of battle, and the zouaves were hastening into line, when I received an order to detach a regiment for the support of Rickett's battery (of Fraklin's brigade), posted on a hill a quarter of a mile to our right and front, near Dogan's house. I led up the zouaves for this important service, leaving the Thirty-eighth under its gallant and experienced colonel, Hobart Ward. Ricketts was soon ordered to take a new position near the Robinson house. The zouaves followed in support, and finally formed line on the right flank of the battery, with two companies in reserve.

Up to this time the enemy had fallen back, but now he formed the remains of his brigade engaged with Hunter in the morning, viz, Bee's, Barton's, and Evans', in a new line, upon Jackson's brigade of fresh troops, making altogether 6,500 infantry, 12 pieces of artillery, and Stuart's Cavalry, according to General Beauregard's report. This force was posted in the belt of woods which skirted the plateau southwardly, and lying in the angle formed in that direction, between the Warrenton and Sudley roads, about a mile from the Warrenton road, and with its left resting on the Brentsville and Sudley road.

Ricketts' battery had crossed the Sudley road from its post near Dogan's house, and was within musket-range of the woods, which stretched from that road around from his right towards his front, and forming a pocket, which almost enveloped the battery, with its support.

The enemy were first discovered by Colonel Heintzelman lining the woods in our front. He ordered up the zouaves, commanded by Colonel Farnham. The ground was slightly rising before us, and the enemy opened a heavy but not destructive fire as we reached the crest. The zouaves returned the fire, but immediately fell back, bewildered and broken. Stuart's Cavalry charged upon them from the woods on the right, but were scattered by a fire from the two reserve companies, with a loss (ascertained from the Southern papers) of twenty-nine killed and wounded. Meantime Rickett's cannoneers were being joined off. With Colonel Heintzelman's approval, and a promise of re-enforcements, I collected some one hundred zouaves, and, with Captain Downey and others of their officers, made a dash into the woods on our right, and killed, wounded, and captured about thirty of the enemy. Returning in a few minutes, I found the field cleared of both friends and foe, except