We seem not to have noticed that the world has already reached the point that war is, in fact, not in vogue as a "way for nations to resolve disputes."
Look at the "wars" that are being waged at this moment. The U.S. against... well, against a vaguely defined but definitely transnational group of terrorists. Terrorism is not war, and neither is an action to suppress it. We've got some battles going on in Africa, but if that's what war has devolved into, it won't be long before it's extinct. Chaotic, poorly funded, waged primarly against civilian targets, it has more in common with terrorism than with true warfare.
The U.S. was at war with Iraq, but only for an eyeblink before we defeated a hopelessly inferior enemy force. That wasn't so much warfare as bullying. Ditto for Afghanistan, and in that case we even admitted that we were making "war" on the Taliban, not the whole country.
What was the last real honest-to-Ares war? Our previous bullying of Iraq over its bullying of Kuwait? The five-sided donnybrook in the former Yugoslavia? The flyweight stalemate between Iraq vs. Iran?
Yes, I suppose any of those could be called war and it would be an insult to the people who died therein to deny them that strange sort of honor.
But still... Sixty years ago we had just finished a war that killed tens of millions of people, involved nuclear weapons, and resulted in the abject destruction of two of the world's most powerful nations and a complete reorganization of global politics.
Then Korea, Vietnam, the Arab-Israeli War.
Then Bosnia, Somalia, Chad, Afghanistan, Iraq.
I see a trend here. I don't think that nations are finding war to be the ultimate way to resolve disputes any more. For one thing, the most recent wars haven't really resolved anything.
We now have violence on a much smaller scale. Terrorism. All in all, a vast improvement.