In his standard reference work on the Civil War, Generals in Blue, Ezra Warner declared George B. McClellan (1826--1885) one of the most controversial figures in American military history. In this revealing book, Thomas W. Cutrer provides the definitive edition of McClellan's detailed diary and letters from his service in the Mexican War (1846--1848), during which he began the rise that culminated in his being named general in chief of the Union...