Maj. Jed. Hotchkiss, Confederate Military History, a library of Confederate States Military History: Volume 3, Virginia
Clement Anselm Evans, Ed.

[102] cross Bull run at Sudley ford, turn the Confederate left, and get in its rear between Bull run and the Manassas Gap railroad, hoping by so doing to prevent Johnston from joining Beauregard. This plan of engagement adopted, McDowell intended to begin his movement during the night of the 20th, but his division commanders persuaded him to put it off until the morning of the 21st. Schenck's and Sherman's brigades of Tyler's division, with Carlisle's battery of six brass guns and a 30-pounder Parrott gun, marched at 2:30 a. m. of the 21st from near Centreville, along the Warrenton road to near the stone bridge over Bull run, where Schenck deployed his brigade on the left of the road and Sherman's on the right, with artillery in the Warrenton road and in that leading to Blackburn's ford, and opened at 6:30 a. m. on the Confederate left with all his guns, but brought no reply, as the Confederate guns were of too short range. This disconcerted McDowell, leading him to fear an attack from Blackburn's ford, and caused him to hold back one of Heintzelman's brigades in reserve to Schenck. Later, as Schenck's skirmish line advanced, it was met on the eastern side of Bull run by that of the Confederates. About 7 Beauregard ordered Jackson's brigade, the nearest reserve force, to move with Imboden's Staunton artillery and Walton's battery to the left to support Cocke as well as Bonham; the brigades of Bee and Bartow, under the former, were also sent to support the left against the threatened attack by Schenck.

In the meantime, the main Federal column continued its flanking movement by Sudley ford, but losing time in wading across as the men halted to drink. Seeing clouds of dust rising in the direction of Manassas Junction, indicating the coming of a large force that might head off his movement, McDowell ordered the heads of regiments to break from the columns and march forward, separately, as rapidly as possible; directed Heintzelman's reserve brigade to cross the fields on the left to a nearer ford below Sudley, and sent word to Tyler to hurry up the advance. The brigades of Burnside and Porter, with Griffin's battery, had already passed through the Sudley wood, which Jackson made famous the next year, and were deploying, facing southward, on the sloping open of cultivated ground beyond; and immediately behind these were marching the brigades of Franklin and Wilcox,