a 'secret weapon' that it didn't realize it had. What the South should have done, in the late 1850's, is to have realized that slavery was a dying institution anyway and that it could get by for the time being with half or a third less slaves than it had. The South could have granted immediate freedom to half of its slave population with the condition that after manumission they couldn't remain in the
South, but would have to move up North. If politically astute, the South could have 'spun' this relocation requirement as simply a way of spreading 'diversity' to the North.
With this, the abolitionist movement up North would have stopped 'dead in its tracks', in my opinion, and over 700,000 lives would have been saved, and all slaves would have been gained freedom anyway before 1900 due to international pressure.