Numbers 10. Reports of Colonel Nathaniel C. McLean, Seventy-fifth Ohio Infantry, commanding Second Brigade, of the battles of Groveton and Bull Run.

HDQRS. SECOND BRIGADE, FIRST DIVISION,
Camp at Centerville, September 1, 1862.

GENERAL: I have the honor to report, so far as concerning the active participation of the Second Brigade in the battle of August 30, as follows:

The brigade had been placed in position on the evening of August 29, with the left resting on the Warrenton road, and remained there until the afternoon of August 30, when by order I detailed the Fifty-fifth Ohio Regiment to occupy a position on the left of the Warrenton road, was pointed out to Colonel Lee by an aide of General Sigel, the object of which was to keep up a connection with General Reynolds on my left. A short time after General received an order in my presence from General Pope, delivered by Colonel Ruggles, to place a battery with a brigade on a bald to my left, so as sustain General Reynolds, and I was immediately ordered by General Sigel to that position a battery of four pieces artillery and the Second Brigade. The order was executed by placing the battery with the three remaining regiments of the brigade (the Seventy-third Ohio, the Twenty-fifth Ohio, and the Seventy-fifth Ohio) in the position indicated, so as to sustain General Reynolds, who then with his right wing joined my left. Soon after I had taken this position, much to my surprise General Reynolds put his troops in motion and marched entirely past and across my front to the right, to what point I am not informed. Finding that this movement had entirely exposed my left flank I immediately changed the position of my troops, and deployed in line of battle the Seventy-third and Twenty-fifth Ohio Regiments, fronting the west and to the left of the battery, and the Seventy-fifth and Fifty-fifth Ohio, then returned from its former position on the right of the battery, thus making my line of battle fronting the west, with the battery in the center and two regiments on each side. I could by this time see the enemy advancing on my front and a little to the right, driving before them a regiment of Zouaves. They came on rapidly, when some troops advanced to meet them from behind a hill on my right. These troops were also driven back in confusion, and as soon as they got out of the way I opened upon the enemy with the four pieces of artillery, throwing first shell, and as they approached nearer, canister. I also commenced a heavy fire with infantry, and in a short time the enemy retreated in great confusion. During this time my attention had been called to a body of troops advancing toward my position in the rear of my left flank, and supposing them to be enemies, I gave the order to turn two pieces of artillery upon them, but countermanded it upon the assurance of some one who professed to know the fact that they were our own troops, and I readily believed this, as their clothing was dark, and then rested easy, thinking re-enforcements were coming to take position on my left and occupy the place vacated by General Reynolds. I then turned my exclusive attention to the enemy on my front. Soon after this a heavy force of the enemy, much superior to my own, marched out of the woods across the position formerly occupied by General Reynolds, in front of my left flank, and swept around, so as to come in heavy force both on the front and flank of my left wing. This force opened a heavy fire upon the Seventy-third Ohio, and the