Robert E. Lee knew that he had to keep the momentum of the Confederate forces moving forward, bringing the Army of Northern Virginia and the war itself northward into Union territory. A decisive string of victories might embolden foreign allies to join the Confederacy's fight.On September 13, a piece of paper marked Special Orders No.191 fell into Union General McClellan's hands. On it was a message from Lee to his generals detailing his master plan for opening an invasion of the North...but could it be trusted?This is the story of the battle of Antietam and the events leading up to the fateful day where Union casualties topped 12,000 and Confederate casualties topped 11,000, where not just such memorable figures of military history as Lee and McClellan, but also Burnside, Longstreet, Hooker, and Jackson all took part.