Beauregard has now 21,833 men, and 29 pieces of artillery of his own "Army of the Potomac." Johnston's and Holmes's junction with him has raised the Rebel total to 32,000 effectives, and 55 guns. McDowell, on the other hand, who started with 30,000 effectives, finds himself on the 19th—owing to the departure of one of his regiments and a battery of Artillery, because of the expiration of their term of enlistment,—with but "28,000 men at the utmost."—[Comte de Paris.]
On the evening of Saturday, the 20th of July, Johnston and Beauregard hold an important consultation. The former feels certain that Patterson, with his more than 20,000 effectives, will now lose no time in essaying a junction with McDowell's Army, and that such junction will probably be effected by July 22nd. Hence he perceives the necessity of attacking McDowell, and if possible, with the combined Rebel Forces, whipping him before Patterson can come up to his assistance.
At this consultation it is agreed by the two Rebel generals to assume the offensive, at once. Beauregard proposes a plan of battle—which is an immediate general advance of the Rebel centre and left, concentrating, from all the fords of Bull Run, upon Centreville, while the Rebel right advances toward Sangster's cross-roads, ready to fall either on Centreville, or upon Fairfax Court House, in its rear, according to circumstances.
The plan proposed, is accepted at once by Johnston. The necessary order is drawn up by Beauregard that night; and at half past four o'clock on Sunday morning, July 21st, Johnston signs the written order. Nothing now remains, apparently, but the delivery of the order to the Rebel brigade commanders, a hurried preparation for the forward movement, and then the grand attack upon McDowell, at Centreville.
Already, no doubt, the fevered brain of Beauregard pictures, in his vivid imagination, the invincible thunders of his Artillery, the impetuous advance of his Infantry, the glorious onset of his Cavalry, the flight and rout of the Union forces, his triumphal entry into Washington—Lincoln and Scott and the Congress crouching at his feet—and the victorious South and conquered North acclaiming him Dictator! The plan is Beauregard's own, and Beauregard is to have command. Hence all the glory of capturing the National Capital, must be Beauregard's. Why not? But "man proposes, and God disposes." The advance and attack, are, in that shape, never to be made.
McDowell, in the meantime, all unconscious of what has transpired in the Shenandoah Valley, and between there and Manassas; never dreaming for an instant that Patterson has failed to keep Johnson there—even if he has not attacked and defeated him; utterly unsuspicious that his own lessened Union Army has now to deal with the Forces of Johnston and Beauregard combined—with a superior instead of an inferior force; is executing a plan of battle which he has decided upon, and announced to his general officers, on that same Saturday evening, at his Headquarters in Centreville.
Instead of attempting to turn the Enemy's right, and cut off his communications with Richmond and the South, McDowell has now determined to attack the Enemy's left, cut his communication, via the Manassas Gap railroad, with Johnston's Army,—still supposed by him to be in the Valley of the Shenandoah—and, taking him in the left flank and rear, roll him upon Manassas, in disorder and defeat—with whatever might follow.
That is the plan—in its general features. In executing it, Blenker's Brigade of Miles's Division is to remain at Centreville as a reserve, throwing up intrenchments about its Heights, upon which to fall back, in case of necessity; Davies's Brigade of the same Division, with Richardson's Brigade of Tyler's Division—as the Left Wing—are to demonstrate at Blackburn's Ford, toward the Enemy's right; Tyler's other three brigades, under Keyes, Schenck, and Sherman, are to feign an attack on the Enemy's left, posted behind the strongly-defended Stone Bridge over which the Warrenton turnpike, running Westward, on its way from Centreville to Warrenton, crosses Bull Run stream; while the strong divisions under Hunter and Heintzelman—forming McDowell's Right Wing—are to follow Tyler's Division Westward down the turnpike to a point within one mile and a half of the Stone Bridge, thence, by cross-road, diverge several miles to the North, then sweep around gradually to the West, and then Southwardly over Bull Run at Sudley Springs Ford, swooping down the Sudley road upon the Enemy's left flank and rear, near Stone Bridge, rolling it back toward his center, while Tyler's remaining three brigades cross the bridge and join in the assault. That is the whole plan in a nutshell.
It has been McDowell's intention to push forward, from Centreville along the Warrenton Pike a few miles, on the evening of this Military conference; but he makes his first mistake, in allowing himself to be dissuaded from that, by those, who, in his own words, "have the greatest distance to go," and who prefer "starting early in the morning and making but one move."
The attacking divisions now have orders to march at 2:30 A. M., in order "to avoid the heat," which is excessive. Tyler's three immediate brigades—or some of them—are slow in starting Westward, along the Warrenton Pike, to the Stone Bridge; and this leads to a two or three hours delay of the divisions of Hunter and Heintzelman, before they can follow that Pike beyond Centreville, and commence the secret detour to their right, along the cross-road leading to Sudley Springs.