On September 17, 1862, the Union and Confederate armies clashed in Sharpsburg, Maryland.Twelve hours later, more than 23,000 soldiers were dead or wounded -- marking the end of the bloodiest day in American history.It was the battle the Confederacy hoped would break the back of the enemy for good. It was a bold incursion into northern territory the Union dared not let stand. For Robert E. Lee, it was a moment in time when he would be called upon to offer up the supreme sacrifice. For General A. P. Hill, it was a chance to avenge a betrayal by his former West Point roommate, Union commander George McClellan. For a young adjutant of Stonewall Jackson, it was a lesson in the true savagery of war; for an ambitious newspaper reporter it was the scoop of the century. And for President Abraham Lincoln, haunted by war's carnage and intense personal tragedy, it was the victory he needed to make the dream of freedom a reality.