Had McClellan not absurdly overestimated the number of troops opposed to him when his army neared Sharpsburg on the 15th of September, 1862, he might have defeated Lee and possibly destroyed or captured his entire force. Never before had a Union commander had such an opportunity to deliver a crushing blow. He had more than 80,000 men under his control--fully twice as many as his adversary; he had the Confederate plan of campaign in his hands and such fighting as had occurred with the exception of that at Harper's Ferry had been decidedly in his favor. Moreover, Lee had recently met with a serious accident, his horse having knocked him down and trampled on him, breaking the bones of one hand, and otherwise injuring him so severely that he had been obliged to superintend most of the posting of his army from an ambulance. By a curious coincidence, too, "Stonewall" Jackson had been hurt in a similar manner a few days previously, so that if the battle had begun promptly, it is highly probable that he, too, would have been physically handicapped, and it is certain that his troops could not have reached the field in time to be of any assistance. To Lee's immense relief, however, McClellan made no serious attack on either the 15th or 16th of September, but spent those two days in putting his finishing touches on his preparations, and before he completed them that Opportunity "which knocks but once at each man's gate" had passed him by, never to return. The battle of Antietam or Sharpsburg began at dawn of the 17th, but by that time Jackson had arrived and both he and Lee had so far recovered from their injuries that they were able to be in the saddle and personally direct the movements of their men. The Confederate position had been skillfully selected for defense on the hills back of Antietam Creek and McClellan's plan was to break through his opponent's line, gain his rear and cut him off from retreat. But Lee, who had closely watched the elaborate massing of the Union forces for this attempt, was fully prepared for it and the first assault against his line was repulsed with fearful slaughter. No subtle strategy or brilliant tactics of any kind marked McClellan's conduct of the battle. Time and again he hurled his heavy battalions against his opponent's left, center and right in a desperate effort to pierce the wall of gray, and once or twice his heroic veterans almost succeeded in battering their way through. But at every crisis Lee rose to the emergency and moved his regiments as a skillful chess player manipulates his pieces on the board, now massing his troops at the danger point and now diverting his adversary's attack by a swift counter-stroke delivered by men unacquainted with defeat. Both his hands were heavily swathed in bandages and far too painful to admit of his even touching the bridle rein, but he had had himself lifted into the saddle and for fully fourteen hours he remained mounted on "Traveller," his famous war horse,