The American Civil War
The bloodiest war in American History.
Contrary to popular belief, Abraham Lincoln was NOT a good leader. In fact, he was such a poor leader, that half of the nation seceded! By my measurement, that makes a poor leader, because it means his followers definitely were not following him.
South Carolina seceded from the Union because Lincoln was elected. It's possible that South Carolina may have seceded anyway; but that's also hypothetical. It's a fact that South Carolina was the first state to secede because of Lincoln's election.
The reason that South Carolina would not follow Lincoln's leadership had a lot more to do with politics than the President's personal character. It's true that Lincoln was not in favor of slavery. But he was NOT against slavery. He would have protected slavery as an institution if he thought it would hold together the Union. In fact, he did protect slavery for a long time.
In Missouri, General John C. Fremont pronounced all slaves of the secessionists free. Lincoln ordered Fremont to rescind the pronouncement. Let me repeat that, because it's important: Fremont abolished slavery in Missouri, and Lincoln told him to take it back. Fremont refused and Lincoln removed him from duty. Abraham Lincoln was protecting slavery as an institution, for the sole reason that he thought abolition was to radical and extreme of a movement.
Of course, it was an extreme movement. It was so extreme that South Carolina seceded just thinking that Lincoln might do something like that. They fulfilled their own prophecy.
What started the war?
Jefferson Davis, president of the Confederate States ordered General Gustav P.T. Beauregard to seize Fort Sumter in Charleston Harbor, South Carolina. The reason he picked this particular fort is because Lincoln was sending a supply and relief party to reinforce the fort.