On the 20th the advance of the corps (General Kearny's division) commenced to embark for Aquia Creek, rapidly followed by the rest of my troops. Off Aquia Creek I received orders changing my destination to Alexandria. I arrived at Alexandria at 1.30 p.m. on the 22nd, and met on the wharf Major Key, of General Halleck's staff, with orders to hurry forward my corps to the support of General Pope. Part of General Kearny's division left in the cars that afternoon, soon followed by my whole force. On the 26th my troops were all in the vicinity of Warrenton Junction. At dark I received orders to occupy Weaversville and vicinity, and also learned that the enemy had possession of the railroad in our rear. General Pope directed me to send a regiment and drive them back. This regiment found the enemy in force and fell back.

The next morning, the 27th, General Hooker was ordered as far as Bristoe Station, and to advance the day after that to Greenwich, General Kearny's division to take a left-hand road and follow General Reno's division toward Greenwich. I was detained at Warrenton Junction till 3 p.m. to accompany General Pope. When we reached Bristoe Station the enemy had, after a sharp engagement, retreated toward Manassas Junction. They belonged to General Ewell's division.

Our troops behaved with their usual gallantry. Our loss was some 300 men, mostly of the Excelsior Brigade. At Bristoe Station we found the remains of two locomotives and trains of cars that the enemy had burned. In places the rails and cross-ties had been torn up, culverts destroyed, and bridges burned. I am still without General Hooker's report and that of the Second Brigade.

The next morning, August 28, General Kearny's division advanced on Manassas Junction, followed by General Hooker's as a reserve. About noon General Kearny reached the Junction. Our railroad trains fired by the enemy were still burning. We here learned that he had retreated on Centreville and was 30,000 strong. The pursuit was continued. The advance of General Kearny's division found but one regiment of rebel cavalry at Centreville, which fell back at his approach.

We now learned that the enemy had fallen back on the Warrenton turnpike. General Kearny's division encamped near Centreville, between there and Bull Run. General Hooker's division encamped on the south side of Bull Run.

At 11 p. m. I received instructions that General McDowell had intercepted the retreat of the enemy, and that General Kearny's division was ordered to advance at 1 a.m. until he met the enemy's pickets, there to await daylight, and for me to follow at daylight with General Hooker's division. From some cause to me unknown General Kearny's division had not moved at daylight. I ordered it forward and he soon joined it.

At 10 a.m. I reached the field of battle, a mile from stone bridge, on the Warrenton turnpike. General Kearny's division had proceeded to the right and front. I learned that General Sigel was in command of the troops then engaged and called on him.

At 11 a.m. the head of Hooker's division arrived; General Reno an hour later. At the request of General Sigel I ordered General Hooker to place one of his brigades at General Sigel's disposal to re-enforce a portion of his line then hard pressed. General Grover reported, and before long became engaged, and was afterward supported by the whole division. General Pope arrived between 1 and 2 p.m. The enemy were driven back a short distance toward Sudley Church, where they made another stand, and again pressed a portion of our line back. All