If his force is overwhelming I shall retire to the Rappahannock Railroad Bridge, saving my command for defense there and future operations. Please inform Johnston of this, via Staunton, and also Holmes. Send forward any re-enforcements at the earliest possible instant and by every possible means.

G. T. BEAUREGARD.

HDQRS. FIRST CORPS, ARMY OF THE POTOMAC, Manassas, August-, 1861.

GENERAL: With the general results of the engagement between several brigades of my command and a considerable force of the enemy in the vicinity of Mitchell's and Blackburn's Fords, at Bull Run, on the 18th ultimo, you were made duly acquainted at the time by telegraph, but it is my place now to submit in detail the operations of that day.

Opportunely informed of the determination of the enemy to advance on Manassas, my advanced brigades, on the night of the 16th of July, were made aware from these headquarters of the impending movement, and in exact accordance with my instruction (a copy of which is appended, marked A), their withdrawal within the lines of Bull Run was effect, in face of an in immediate proximity to a largely superior force, despite a well-planned, well-executed effort to cut off the retreat of Bonham's brigade first at Germantown and subsequently at Centreville, whence he withdraw by my direction after midnight without collision, although enveloped on three sides by their lines. This movement had the intended effect of deceiving the enemy as to my ulterior purposes, and led him to anticipate an un resisted of Bull Run.

As prescribed in the first and second section of the paper herewith, marked A, on the morning of the 18th of July, my troops, resting on Bull Run from Union Mills Ford to the stone bridge, a distance of about eight miles, were posted as follows:

Ewell's brigade occupied a position in vicinity of the Union Mills Ford. It consisted of Rodes' Fifth and Seibels' Sixth Regiment of Alabama,and Seymours' Sixth Regiment Louisiana Volunteers, with four 12-pounder howitzers of Walton's battery, and Harrison's, Green's, and Cabell's companies of Virginia Cavalry.

D. R. Jones' brigade was in position in rear of McLean's Ford, and consisted of Jenkins' Fifth South Carolina and Burt's Eighteenth and Featherston's Seventeenth Regiments of Mississippi Volunteers, with two bars 6-pounder guns of Walton's battery, and one company of cavalry.

Longstreet's brigade covered Blackburn's Ford, and consisted of Moore's First, Garland's Eleventh, and Corse's Seventeenth Regiments Virginia Volunteers, with two 6-pounder brass guns of Walton's battery.

Bonham's brigade held the approaches to Mitchell's Ford. It was composed of Kershaw's Second, Williams' Third, Bacon's Seventh, and Cash's Eighth Regiments South Carolina Volunteers; of Shields' and Del. Kemper's batteries, and of Flood's, Radford's, Payne's, Ball's, Wickham's, and Powell's companies of Virginia Cavalry, under Colonel Radford.

Cocke's brigade held the fords below and in the vicinity of the stone bridge, and consisted of Withers' Eighteenth, Lieutenant-Colonel Strange's Nineteenth, and R. T. Preston's Twenty-eight Regiments,