By effective range is meant the distance where, under ordinary conditions, the enemy’s losses are sufficient to stop his advance.  The effective range of Brown Bess was about 60 yards.  The American rifled artillery was effective, in clear weather, at 2000 yards, the 12-pounder smooth-bore at 1600, the 6-pounder at 1200.)

The Confederates, along the banks of Bull Run, disposed of 26,000 infantry, 2500 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,* was better adapted for defence than for attack. (* O.R. volume 2 page 505.) 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 manoeuvre 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.