Editor's Note: This column was coauthored by Bob Morrison. President Abraham Lincoln had been warned by Gen. George B. McClellan not to interfere with the institution of slavery. McClellan was a “War Democrat,” willing to fight to preserve the Union, but unwilling to do anything about the root cause of the rebellion that threatened the life of the nation. Ironically, it was McClellan’s victory at the Battle of Antietam on September 17, 1862, that had given Lincoln the opportunity he needed to issue his Preliminary Emancipation Proclamation. In that document, the President warned rebellious states in the South that they...