Alexander Gardner, The Battle of Antietam, 17 September 1862
Lee was ultimately forced to fight at Antietam (Sharpsburg). It was the bloodiest single day of the entire war, during which Lee faced frightening odds—his twenty-four brigades were confronted by forty-four. He lost one third of his men. This battle was watched by both photographers and foreign observers. When Lee withdrew; the chance of foreign intervention on behalf of the Confederacy vanished with him.
Photograph courtesy of the Library of Congress