Last night I watched a TV program on the Surrender of the Confederacy. Gary Gallagher ably made the point that the Confederates fought on until they had no alternative. The Confederate economy was in ruins, the slaves who formed the basis of that economy were departing in droves, the Confederate military losses were huge and Lee's army had finally been defeated and surrendered, and the civilian population had undergone hardships and accepted governmental regimentation that could scarcely have been imagined before the Civil War had begun.
I have long wondered how the leaders of the southern states that seceded from the Union could have made so grave a mistake as to lead their people to secession and Civil War, given that it had that outcome. One answer, of course, is that they assumed that their brave young men would have quick success in the field, that the people of the states remaining in the Union would quickly lose heart, and that European powers would come to the aid of the Confederacy as they had come to the aid of Washington during the Revolutionary War.
It seems obvious from the 21st century that had the Confederacy not been formed and the Civil War fought, a better option could have been found. Perhaps slavery could have been abolished more gradually, without war, and in such a way that the economy of the southern states was less damaged. For example, perhaps there could have been some payment made to the owners of the slaves who were emancipated, and certainly there would have been less war damage and fewer people killed, disabled and injured.
It occurs to me that another answer to how the Civil War came to be is in the nature of the decision making involved. In January 1861, as states began to chose whether to form a Confederacy or stay in the Union, there were 34 states. Seven of these seceded from the Union before April 15, 1861 and four more (Arkansas, Tennessee, North Carolina and Virginia) after that date; 23 remained in the Union. Of particular concern were several border states where slavery was still legal, which chose to remain with the Union, even though a number of their residents volunteered to fight for the Confederacy. (West Virginia was not a state in 1861, becoming a state during the Civil War when it seceded from Virginia and was accepted as a state by the Union.)
When South Carolina, the first state to secede, chose to do so, it had no way of knowing how many other states would join it. It would not have been difficult to guess, however, that the Confederacy if it were to be formed at all, would be formed by states that still maintained the institution of slavery -- a total of 14, with a smaller population and less industrial capacity than the 23 states that had already abolished slavery. Still, the South Carolina leaders could not be sure what would be decided by their sister states.
What if only one or two other states had joined South Carolina in secession? I suppose that so small a group would have realized that they had no chance, and would have reached some accommodation. The leaders of those states would have been repudiated, they would have remained in the Union, and (one hopes) some peaceful solution would have been found to the abolition of slavery.
What if Arkasas, Tennessee, North Carolina and Virginia had chosen to stay in the Union? There was no way to know as the first states were voting to secede whether they would or world not. Perhaps there would have been a shorter war, certainly less destructive to those four states.
If the three border states that remained in the Union had instead chosen to joint the Confederacy, perhaps the cost of the war would have been so much greater to the Union that it would have been more willing to agree to a "two state solution". Perhaps the European powers would have been more willing to openly support the Confederacy. Who knows?
Today, it might be possible to make precise estimates of the likely behavior of the scores of political bodies making decisions, and of the relative military capacity of the likely combatants. I can not imagine that that was possible in 1860. While it seems clear today that the institution of slavery was evil, and that it would eventually be abolished in the modern world, it did not seem equally clear to the plantation owner class of the South in 1860.
There is probably a lesson for the modern world in this analysis somewhere.