Many things happened since the last world war. To name the few, Nürnberg process, the Universal Declaration of Human Rights, introducing the MAD doctrine backed up by the Math Game theory, coining the European Union, passing away of Communism in USSR and China.
You know, you'll only go on trial for war crimes if you lose.

As for the Universal Declaration of Human Rights, if you don't have any means to enforce it, then it has no impact on the real world. We have at this very moment a lot of conflict on this planet, a lot of human rights violations (even in the First World), a great lot of famine and plagues and too many other atrocities to mention. What does the UDHR do for the people involved? Absolutely nothing. It's like saying you have a right to own your home, but you're not allowed to defend it and there's no police around.
As for the European Union, it's vastly overrated: it has no credible military force of its own against a serious opponent, and so far it didn't do much for the Ulster and Basque question. It doesn't even police its own borders much, given the boatloads of people that are crossing the Mediterrean, so much that Italy had to sign an agreement to send them back to Libya where we don't want to know what might happen to them.
The MAD doctrine made sense when you had two blocks with enough strategic weapons to make it feasible. What do you do in a world of asymmetric warfare?
And as for Communism, much as it's a warped ideology it has ruled for about 80 years. That's peanuts in the history of the world. Mind you, feudal Europe and Japan made perpetual warfare an art when everybody pretty much had the same government system, religion and ideology.[/QUOTE]
No mad leader would ever plunge his country into barbarism again, given it's a country with a substantial economy and it takes part in sustaining the world's order.
Mad leaders do not scare me. Apparently sane ones, however, are quite terrifying. By the way, we've made it possible to wage war without affecting to much our precious quality of life back home, so be assured that war is here to stay, in a form or another.