Face to face with this desperate crisis, McClellan, who had been practically removed from command, was restored to duty and given charge of all the Union forces in the field. Had he been invested with supreme authority, at least one grievous blunder might have been avoided, for as he proceeded to the front, calling loudly as usual for reënforcements, he advised the evacuation of Harper's Ferry, garrisoned by some 12,000 men who were exposed to capture by Lee's advance on Frederick City. But Halleck rejected this advice and on September 15, 1862, "Stonewall" Jackson, with about 20,000 men, swooped down upon the defenseless post and gobbled up almost the entire garrison with all its guns and stores. To accomplish this, however, he was forced to separate himself from Lee, and while McClellan, with over 87,000 men, was protesting that his opponent had 120,000 and that it was impossible to win against such odds, Lee's strength had been reduced to about 35,000 and his safety absolutely depended upon his adversary's fears. It was hardly to be hoped, however, that McClellan's imagination would cause him to see three men for every one opposed to him, but such was the fact, and even when one of Lee's confidential orders fell into his hands, revealing the fact that Jackson's whole force was absent, he still thought himself outnumbered. The discovery of this order was a serious blow to Lee, for it not only exposed his immediate weakness, but actually disclosed his entire plan. How it was lost has never been explained, for its importance was so fully realized that one of the officers who received a copy pinned it in the inside pocket of his coat, another memorized his copy and then chewed it up and others took similar precautions to protect its secret. Some officer, however, must have been careless, for when the Union troops halted at Frederick City, through which the Confederates had just passed, a private in an Indiana regiment found it lying on the ground wrapped around some cigars and, recognizing its value, carried it straight to his superiors who promptly bore it to Headquarters. Had Lee remained ignorant of this discovery it is possible that McClellan might have effected the capture of his army. But a civilian, favoring the South who happened to be present when the paper reached Headquarters, slipped through the Union lines and put the Confederate commander on his guard. Lee had already noted that McClellan was moving toward him at unusual speed for so cautious an officer and, this was readily explained by the news that his plans were known and Jackson's absence discovered. He accordingly posted his troops so that he could form a junction with the rest of the army at the earliest possible moment and halted in the vicinity of Sharpsburg near Antietam Creek. Chapter XVIII. -- The Battle of Antietam or Sharpsburg