It took a literal civil war, which you don't read about in history books so much because it's not beneficial for the owners of those publishing houses to have more people hear about it. Lots of people died on both sides.

> which you don't read about in history books so much

Just to clarify, are we referring to the American Civil War? The reason I ask is that the idea that it is not a topic that is broadly covered in history books and discussed at depth all throughout schooling is simply false.