...o contend with him beyond the Blue ridge (here called the South mountain), in the vicinity of Hagerstown, if he could draw him that far away, where, at the same time, he could threaten an invasion of Pennsylvania , which was one of the cherished designs of Stonewall Jackson. The one obstacle to delay this movement was the Federal garrison, of some 12,000 men, holding Harper's Ferry, with outposts at Martinsb...