The discovery of Robert E. Lee’s Special Orders No. 191 outside of Frederick, Maryland, on September 13, 1862, is one of the most important and hotly disputed events of the American Civil War. For more than 150 years, historians have debated if George McClellan, commander of the Union Army of the Potomac, dawdled upon receiving a copy of the orders before advancing to challenge Lee’s forces at the Battle of South Mountain.

In this detailed new study, authors Gene Thorp and Alexander Rossino exhaustively document how ‘Little Mac’ rapidly reorganized his army, advanced on Frederick with more speed than previously thought, and then moved with uncharacteristic energy to take advantage of Lee’s divided forces. These actions enabled McClellan to strike a blow that wrecked Lee’s plans for a decisive battle on his own terms and sent the Army of Northern Virginia reeling back toward the Potomac River.

The Tale Untwisted: General George B. McClellan, the Maryland Campaign, and the Discovery of Lee’s Lost Orders proposes a rich, new interpretation of the fate and impact of the Lost Orders on the history of the 1862 Maryland Campaign.