It was decided therefore to advance the army and bring on the hazardous battle against the better judgment of every trained military man at Washington.
General Scott was still in supreme command of the army, but he was much too old and too feeble to conduct the perilous enterprise in person. General Irwin McDowell was chosen to plan the battle and fight it. He had never commanded an army before or conducted a campaign, but neither had any other officer then available, and his technical knowledge of strategy was thorough. On this occasion his plan of battle was admirable, one of the best, General Sherman has said, that was formed at any time during the war. It was essentially identical with that afterwards adopted by General Lee at the Seven Days' Battles and again at Chancellorsville.
A reconnoissance in force was made against the Confederate lines along Bull Run on Thursday, the eighteenth of July, which disclosed the fact that the Confederates were fully entrenched in a strong position which commanded the crossings of the stream and the plateau over which it must be approached.
Having found out all this, General McDowell decided to bring on a battle on Sunday, July the twenty-first.
It is not the purpose of the present writer to tell the story of Manassas or that of any other battle in military detail. That has been done too often already, to the hopeless confusion of the civilian reader's mind. Only an intelligible outline is attempted here, with no effort to locate this or that division or brigade or regiment or battery upon the field or to follow out the details of any movement made by any of them.
Beauregard held his line along the stream known as Bull Run, over a space of several miles. This line had been established in defense of the railroad "junction" at Manassas where the line of the Orange and Alexandria railroad joined that of the Manassas Gap railroad. This position was suggested by the artificial geography of railroad construction. It was defended by the natural physical geography of Bull Run, which furnished the Confederates a comparatively good, though by no means a strategically satisfactory, line of defensive fighting.
McDowell's purpose was to assail the Confederates on their extreme right, there making a feint as if to force a crossing of Bull Run at that point which he did not at all intend; to march his stronger battalions to his own right along roads substantially parallel with Bull Run; here and there to divert a force to the Bull Run line and make fighting there by way of preventing Confederate concentration at any point and finally to hurl all his force with irresistible fury upon the extreme left of the Confederate line, which he intended and confidently expected to turn and overwhelm with his superior numbers.
It was McDowell's plan to deceive the Confederates as to his point of decisive attack, to keep them busy all along the Bull Run line and, late in the day, to envelop their left wing, crush it by superior force, capture the railroad and perhaps compel Beauregard's surrender for lack of a line of retreat.
The plan worked well for a time. The attacks of McDowell's divisions upon the Confederate right and center were stoutly and successfully resisted at every point, but they were made with determination and they served their purpose of deceiving the Southern commander or at least of preventing him from withdrawing heavy forces from that part of the field for the defense of his left against the final and crushing assault which McDowell intended to make there, and in preparation for which he was all day moving his heaviest columns in that direction along roads not visible from the Confederate lines.
When at last that assault was made, it found Beauregard inadequately prepared for it; but, with the determination and energy which were the dominant traits of his character, the Confederate general held his ground obstinately and hurriedly moved troops from the right to the left of his line.