Northern opposition to the Civil War took various forms. Among the more extreme abolitionists, the United States Constitution was considered irretrievably defective and the idea of fighting a war to keep the slaveholding South in the Union under the terms of the Constitution was anathema.
On the other side, the Copperheads believed that the war was simply not worth winning, if possible at all, and that the Union should arrive at the quickest possible settlement on whatever terms the Confederacy was willing to accept.