This is the first biography of Union General William S. Rosecrans in more than fifty years. It tells the story of his military successes and the important results that led to the Union victory in the Civil War: winning the first major campaign of the war in West Virginia in 1861; victories in northeastern Mississippi that made the Vicksburg Campaign possible; gaining the victory without which Abraham Lincoln said the "nation could scarcely have lived over"; conducting two brilliant campaigns in Tennessee and fighting the battle of Chickamauga (giving permanent possession of Chattanooga to the federals); defending Missouri from an invasion in 1864. The book also attempts to explain why Rosecrans was removed four times despite his military successes and examines the important part politics played in the war. Additionally it reveals a man who promoted many advances in medical care, transportation and cartography; a man interested in engineering as well as theology.