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

[98] he could muster barely 18,000 men and 29 guns. In view of this supposed disparity of opposing force, Beauregard urged President Davis to concentrate the armies of Johnston and Holmes with his at Manassas, that he might be ready to fall upon McDowell's flanks, rear, and line of communication, whenever he should advance, cut off his retreat upon Washington, and force him to surrender; and, by so doing, compel Patterson to retreat from the lower Shenandoah valley, and thus insure the capture of Washington. These suggestions were not favorably received at Richmond, and it was intimated to Beauregard that he should retire behind the Rappahannock when an offensive movement of the Federal army began.

Left to his own discretion, Beauregard informed himself fully concerning his position and the approaches to it, destroyed the railroad bridge across Bull run in front of Manassas Junction, and awaited results. A faithful spy, sent to Washington, having reliable information July 15th that the Federal army would march the next day, rode rapidly around the left flank of that army and put this important information in the hands of Beauregard before 9 p. m. of the same day, thus giving him notice of the ordered movement of the Federal army nearly half a day before it began. He at once ordered his outposts back to assigned positions; that from Leesburg, by way of Aldie, by forced marches (28 miles in a day and a half) to Manassas. President Davis was informed of the situation and the suggestion made that the army of the Shenandoah and Holmes' brigade at Aquia creek should be ordered to reinforce Manassas. Davis promptly ordered Holmes to report to Beauregard, and gave Johnston discretion to move his command for the same purpose. The latter, in anticipation of such a call for aid, unhesitatingly consented to this arrangement, and Beauregard, on request, hastened trains up the Manassas Gap railroad to meet the army of the Shenandoah on the way to Manassas Junction and expedite its arrival. At the same time he suggested to Johnston that he concentrate his army at the Aldie gap of the Bull Run mountains, where the turnpikes from the valley through Snicker's gap and Ashby's gap of the Blue ridge unite, and then march southeastward by roads leading to McDowell's line of advance, and fall upon the right and rear of the Federal