[jackpirate]

How about the Mexican-American war, where US soldiers crossed the Mexican border, Mexican troops chased them away, the US decided this was a Mexican invasion, the US declared war, then we took the entire South-Eastern United States from Mexico. All because WE invaded THEM first.

[btilly]

Ah, but it was the Manifest Destiny of the USA to conquer North America and Mexico happened to be in the way. How much more justification do you need?

(Note, I grew up in Canada, which became a single country for mutual defense in case the USA wanted to repeat the incident on its northern border. Details are a bit more complicated than that, but that is the gist of it.)