Before both Napoleon and Wellington an unsound manoeuvre was dangerous in the extreme.  None were so quick to see the slip, none more prompt to profit by it.  Herein, to a very great extent, lay the secret of their success, and herein lies the true measure of military genius.  A general is not necessarily incapable because he makes a false move; both Napoleon and Wellington, in the long course of their campaigns, gave many openings to a resolute foe, and both missed opportunities.  Under ordinary circumstances mistakes may easily escape notice altogether, or at all events pass unpunished, and the reputation of the leader who commits them will remain untarnished.  But if he is pitted against a master of war a single false step may lead to irretrievable ruin; and he will be classed as beneath contempt for a fault which his successful antagonist may have committed with impunity a hundred times over.

So Jackson’s escape from Winchester was not due simply to the inefficiency of the Federal generals, or to the ignorance of the Federal President.  Lincoln was wrong in dispatching McDowell to Front Royal in order to cut off Jackson.  When Shields, in execution of this order, left Fredericksburg, the Confederates were only five miles north of Winchester, and had they at once retreated McDowell must have missed them by many miles.  McDowell, hotly protesting, declared, and rightly, that the movement he had been ordered to execute was strategically false.  “It is impossible,” he said, “that Jackson can have been largely reinforced.  He is merely creating a diversion, and the surest way to bring him from the lower Valley is for me to move rapidly on Richmond.  In any case, it would be wiser to move on Gordonsville."* (* O.R. volume 12 part 3 pages 220, 229 (letter of S. P. Chase).) His arguments were unavailing.  But when Jackson pressed forward to the Potomac, it became possible to intercept him, and the President did all he could to assist his generals.  He kept them constantly informed of the movements of the enemy and of each other.  He left them a free hand, and with an opponent less able his instructions would have probably brought about complete success.  Nor were the generals to blame.  They failed to accomplish the task that had been set them, and they made mistakes.  But the task was difficult; and, if at the critical moment the hazard of their situation proved too much for their resolution, it was exactly what might have been expected.  The initial error of the Federals was in sending two detached forces, under men of no particular strength of character, from opposite points of the compass, to converge upon an enemy who was believed to be superior to either of them.  Jackson at once recognised the blunder, and foreseeing the consequences that were certain to ensue, resolved to profit by them.  His escape, then, was the reward of his own sagacity.

When once the actual position of the Confederates had been determined, and the dread that reinforcements were coming down the Valley had passed away, the vigour of the Federal pursuit left nothing to be desired.