The Confederates, along the banks of Bull Run, disposed of 26,000 infantry, 2,500 cavalry, and 55 guns. Johnston, who had arrived on the 20th, had assumed command; but, ignorant of the country, he had allowed Beauregard to make the dispositions for the expected battle. The line occupied was extensive, six miles in length, stretching from the Stone Bridge, where the Warrenton highroad crosses Bull Run, on the left, to the ford at Union Mills on the right. Besides these two points of passage there were no less than six fords, to each of which ran a road from Centreville. The country to the north was undulating and densely wooded, and it would have been possible for the Federals, especially as the Southern cavalry was held back south of the stream, to mass before any one of the fords, unobserved, in superior numbers. Several of the fords, moreover, were weakly guarded, for Beauregard, who had made up his mind to attack, had massed the greater part of his army near the railroad. The Shenandoah troops were in reserve; Bee’s and Bartow’s brigades between McLean’s and Blackburn’s fords, Jackson’s between Blackburn’s and Mitchell’s fords, in rear of the right centre.
The position south of Bull Run, originally selected by General Lee,[[5]] was better adapted for defence than for attack. The stream, with its high banks, ran like the ditch of a fortress along the front; and to the south was the plateau on which stands Manassas Junction. The plateau is intersected by several creeks, running through deep depressions, and dividing the high ground into a series of bold undulations, level on the top, and with gentle slopes. The most important of the creeks is Young’s Branch, surrounding on two sides the commanding eminence crowned by the Henry House, and joining Bull Run a short distance below the Stone Bridge. That part of the field which borders on Flat Run, and lies immediately north of Manassas Junction, is generally thickly wooded; but shortly after passing New Market, the Manassas-Sudley road, running north-west, emerges into more open country, and, from the Henry House onward, passes over several parallel ridges, deep in grass and corn, and studded between with groves of oak and pine. Here the large fields, without hedges, and scantily fenced, formed an admirable manœuvre ground; the wide depressions of the creeks, separating the crests of the ridges by a space of fifteen or sixteen hundred yards, gave free play to the artillery; the long easy slopes could be swept by fire, and the groves were no obstruction to the view. The left flank of the Confederate position, facing north, on either side of the Manassas-Sudley road, was thus an ideal battle-field.
July 21, 6.30 a.m. Sunday morning, the 21st of July, broke clear and warm. Through a miscarriage of orders, the Confederate offensive movement was delayed; and soon after six o’clock the Federals opened with musketry and artillery against the small brigade commanded by Colonel Evans, which held the Stone Bridge on the extreme left of the Confederate line. An hour later the Shenandoah brigades, Bee’s, Bartow’s, and Jackson’s, together with Bonham’s, were ordered up in support.
8.30 a.m. The attack was feebly pressed, and at 8.30 Evans, observing a heavy cloud of dust rising above the woods to the north of the Warrenton road, became satisfied that the movement to his front was but a feint, and that a column of the enemy was meanwhile marching to turn his flank by way of Sudley Springs, about two miles north-west.
9 a.m. Sending back this information to the next brigade, he left four companies to hold the bridge; and with six companies of riflemen, a battalion called the Louisiana Tigers, and two six-pounder howitzers, he moved across Young’s Branch, and took post on the Matthews Hill, a long ridge, which, at the same elevation, faces the Henry Hill.
Evans’ soldierly instinct had penetrated the design of the Federal commander, and his ready assumption of responsibility threw a strong force across the path of the turning column, and gave time for his superiors to alter their dispositions and bring up the reserves.
The Federal force opposite the Stone Bridge consisted of a whole division; and its commander, General Tyler, had been instructed to divert attention, by means of a vigorous demonstration, from the march of Hunter’s and Heintzleman’s divisions to a ford near Sudley Springs. Part of the Fifth Division was retained in reserve at Centreville, and part threatened the fords over Bull Run below the Stone Bridge. The Fourth Division had been left upon the railroad, seven miles in rear of Centreville, in order to guard the communications with Washington.
Already, in forming the line of march, there had been much confusion. The divisions had bivouacked in loose order, without any regard for the morrow’s movements, and their concentration previous to the advance was very tedious. The brigades crossed each other’s route; the march was slow; and the turning column, blocked by Tyler’s division on its way to the Stone Bridge, was delayed for nearly three hours.