In hindsight, blunders can seem very predictable. Read much history and there will be plenty of times when you can ask, "what on earth were they thinking?".

Books could be written about this, but, yes: Britain had first banned their slave trade in 1807, passed laws ending slavery in the Caribbean in 1834 ( though not completely freeing the enslaved). British millowners were trying to find alternatives to the American South for cotton. A Mississippi plantation owner in 1857 , reading optimistic reports coming from the Cotton Supply Association in England as to the prospects of India supplying British textile mills, could have wondered if it was time to cash out and get into another business. Surely, we can think now, if they had looked forward cotton growers in the South should have at least realized that expanding slavery into other US territories was not likely to be good for the long term.

Looking backwards, though, in 1860 the South had plenty of reasons for confidence. There had been a slave society there for over 200 years, and, since 1830, it had been become extremely profitable. Misgivings over the morality of enslavement were easily smoothed away. Episcopal clergy could point out the existence of slaves in the Bible. Some farmers, like Jefferson Davis, took pride in how "kind" they were to their enslaved workforce. Southern writers loved to compare paternalistic Southern plantation owners with ruthless Northern industrialists. And Southern politicians could claim to have been almost continuously successful: from the Missouri Compromise onwards, they had gotten sympathetic Presidents and won greater and greater concessions for the expansion of slavery into the new territories until finally, with the Dredd Scott decision , they had, they thought, made slavery legal in every state in the union.

Moreover, threats of secession and violence had been quite effective in helping to achieve this. Based on that, in 1860 they had every reason to expect that the Confederate army would succeed in forcing the North ( which was of mixed opinion about abolition, anyway) to negotiate a peace treaty that would again give the South most of what it wanted. And , after that disastrous War, the South would spin a myth that, actually, slavery hadn't really been a bad thing. That it was sometimes done well. There would be proponents of the New South, like Georgia journalist Henry Grady, who would say that the South should industrialize, avail itself of the benefits that would bring- schools, roads, good paying jobs- but the myth of the lovely antebellum South would still be maintained. So, not only did the Southern elites not realize that slavery was unsustainable over the long term before the war, they refused to believe that it had been a bad idea after the war.