War and Majority

As far as the justification of war goes, i'm for it if for no other reason but to justify studing history in school. I don't know if anyone has brought this up yet or not but, as many people know, after WW1 Germany was forced to sign a document that seperated its boundries and greatly reduced their power. Well since no one liked conflict or war that treaty was ignored. By the time Hitler was killing jews it was too late to do anything about it but start another world war, should we let the same thing happen with Irag?