By 1860 the South was an altogether separate nation from the North. The Civil War occurred for exactly the same reason the Revolutionary War occurred: those two peoples did not belong under the same government.

Only a tiny percentage of Southerners owned slaves, but Southerners insisted that as many western states as possible be slave states. The reason for that had nothing to do with their wanting to settle the west with their own slaves. Southerners identified the slave-holding states as THEIR nation.

By exactly the same token, Northerners, who couldn't care less about slaves, considered the free states as the expansion of THEIR nation. There were two nations existing under the same government, and the situation was untenable.

In 1776 the question was whether the British Empire would crush the Americans and truly make them part of the British nation. In 1861 the question was whether the North would crush the South and make it a part of the Yankee Nation.

The Deep South had seceded before Fort Sumter was fired on. Once the war began, the upper South and Texas seceded. They seceded because the two nations were now at war, and their nation was the South. There was a plebiscite in Tennessee and the population there voted three to one to join the Southern Nation. The percentage of slave owners in this overwhelming majority was minuscule.

They voted the way they did because they identified themselves with the Southern Nation.

General Grant made it clear that he was fighting for his nation, not against slavery.

Grant said, "If I thought this war was being fought to abolish slavery, I would offer my sword to the other side."