At Mitchell's Ford, Brigadier-General M. L. Bonham's First Brigade, of four Infantry regiments, two batteries, and six companies of Cavalry.
At Blackburn's Ford, Brigadier-General J. Longstreet's Fourth Brigade, of four Infantry regiments, with two 6-pounders.
At McLean's Ford, Brigadier-General D. R. Jones's Third Brigade of three Infantry regiments, one Cavalry company, and two 6-pounders.
At Union Mills Ford, Brigadier-General R. S. Ewell's Second Brigade, of three Infantry regiments, three Cavalry companies, and four 12-powder howitzers—Colonel Jubal A. Early's Sixth Brigade, of three Infantry regiments and three rifled pieces of Walton's Battery, being posted in the rear of, and as a support to, Ewell's Brigade.
[Johnston also found, on the 20th, the Reserve Brigade of Brig. Gen. T. H. Holmes—comprising two regiments of Infantry, Walker's Battery of Artillery, and Scott's Cavalry-with Early's Brigade, "in reserve, in rear of the right.">[
The disposition and strength of Beauregard's forces at these various points along his line of defense on Bull Run stream, plainly shows his expectation of an attack on his right; but he is evidently suspicious that it may come upon his centre; for, as far back as July 8th, he had issued special orders to the effect that:
"Should the Enemy march to the attack of Mitchell's Ford, via Centreville, the following movements will be made with celerity:
"I. The Fourth Brigade will march from Blackburn's Ford to attack him on the flank and centre.
"II. The Third Brigade will be thrown to the attack of his centre and rear toward Centreville.
"III. The Second and Sixth Brigades united will also push forward and attack him in the rear by way of Centreville, protecting their own right flanks and rear from the direction of Fairfax Station and Court House.