Well, the NT is pretty silent about the subject.
I could of swore I read something about turning the other cheek, loving your enemies, and not taking revenge.
How many are living in a country that would exist if nations hadn't fought?
This is a foolish argument. Every country that exsist today would still exsist without war just under a different name. For example the United States would still be a part of England and would be doing a lot better.