American Civil War
One advantage the Confederacy had was that they only needed to defend their land, whereas the Union could only win if they took full control of the Confederate states. Furthermore, the Union could only fight the war if their people wanted them to keep fighting. Lincoln had opponents in the North (the Copperheads) who wanted the war to end. If the Confederacy had defended itself for long enough, it may have led to more people in the Union turning against the war and supporting the Copperheads. However, Lincoln held on to his support and won the 1864 election.