The Battle of Antietam was a crucial turning point in the American Civil War. This staff ride guide examines the Maryland Campaign and Battle of Antietam, the bloodiest day in American history. On 17 September 1862, the Army of the Potomac met the Army of Northern Virginia on the rolling farmlands around Sharpsburg, Maryland. While General Lee sought to bring the war to the North and "liberate" Maryland, General McClellan, having gained important intelligence, would endeavor to defeat Lee and reverse the momentum of several Union losses. Ted Ballard has once again crafted a definitive battle guide drawing on the Official Records of the War of the Rebellion. Though neither the Union nor the Confederate side gained the decisive victory both desired, the battle provides many lessons in command and control, communications, intelligence, technology versus tactics, and the "fog of war."