Converting the war into an antislavery crusade was a brilliant move on Lincoln’s part, and it resulted in a surge of voluntary recruits into the Union army. But this did not last. Northerners may have disapproved of slavery in the South but, once the bloodletting began in earnest, their willingness to die for that conviction began to wane. […] Lincoln faced the embarrassing reality that he soon would have no army to carry on the crusade.