Previous histories of the Civil War have explained victory or defeat in terms of the skill of commanders, the fighting qualities of the troops, and resources in men and materiel. Intelligence has been largely ignored, not because it wasn't critically important -- Lincoln called it the most difficult problem faced by the Union -- but because so little has been known about it. At the end of the war most of the intelligence records disappeared, and they remained hidden for almost a century, until Edwin Fishel uncovered them during the 40 years of research that has resulted in this monumental book. The Secret War for the Union is unique among Civil War histories in its reliance on original, previously unknown sources. It is the first book to examine in detail the impact of intelligence, and this intelligence explanation alters, sometimes radically, history's understanding of virtually every campaign. Both enthralling and authoritative, The Secret War for the Union is one of the most important books ever published about the Civil War. - Jacket flap.