It's been said countless times before.
It's usually used to discredit any argument for violence to solve a problem.
It has a correlated saying though: "History is written by the victors." Since whoever is left is they ones who will be able to write the history, they will, for all intents and purposes, be right.
Though of course, both sayings are somewhat inaccurate. So yeah, not that useful either way.
So... war determines who is right AND who is left?