On the other hand, the then-US government and its advisors clearly didn't read as much as General Mattis (or read the wrong books), and did not expect to find t

On the other hand, the then-US government and its advisors clearly didn't read as much as General Mattis (or read the wrong books), and did not expect to find themselves embroiled in a bloody civil war. The fact that, as usual, there is not one bad single reason to go to war, but multiple ones, does not mean that acquiring strategic oil supplies was not a significant factor. And of course, spreading freedom and Coca-Cola through shock and awe.