Article Photos: Did battle, and US future, hang on thread of fate?
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This undated image made available by the Library of Congress shows the back side of Confederate Army Gen. Robert E. Lee's Special Order No. 191 dated Sept. 9, 1862. The handwritten document detailed the Southern commander's audacious plans for an invasion of enemy territory that would propel the Confederates to victory. Carelessly left behind as Lee's army marched north, the copy was spotted in a field by Union infantrymen and relayed up the North's chain of command. (AP Photo/Library of Congress)