Richard A. Epstein, the Peter and Kirsten Bedford Senior Fellow at the Hoover Institution
The las paragraph:

No Libertarian Panacea
There are larger lessons to learn from these foreign policy issues. The first is that libertarians, like Chapman and myself, can both be faithful to their basic principles, yet differ strongly on what should be done. The basic principle of libertarian thought is its blanket prohibition against the use of force (including the threat of force) and fraud to achieve personal gain at the expense of others. That principle translates easily into the international context to say that one nation cannot wage war against another.
However easy it is to state that basic principle, it is just that hard to implement it, especially in a world of self-help where there is no common sovereign to stop the use of force. It is easy to allow the use of force in self-defense, but difficult to prevent that excuse from being used by scoundrels for their own ends.
It is even harder to get to the bottom of the simple question of when and where one person (or nation) should come to the assistance of another. The basic legal rule is that such intervention is permissible but not obligatory, and only on behalf of the victim of the attack. The general private law rule that there is no duty to rescue a stranger in a condition of imminent peril from natural forces, even though there is an obvious right to do, carries over to the matter of self-defense.
The great tragedy then is that the clear moral principle can easily become overwhelmed by a series of subsidiary conflicts that extend from difficult factual disputes about the past to uncertain predictions about the future, all set against a background that allows for the exercise of good faith judgment without clear guidelines on how it is best exercised. I do hope that I am wrong, and that the President is doing the right thing. But all things considered, I think that there is a serious risk that his policy of studied disengagement may well turn out, down the road, to drag us into some larger conflict against our will.

More at: http://www.hoover.org/publications/defining-ideas/article/148476
Essentially the little wars and conquests prior to WWII made that war an inevitability. Whereas earlier action by the major powers might have prevented its occurrence though I have to say that it’s unlikely to have had a happy ending, war and civil war were inevitable. It might even have lead to a less pleasant world than the one we live in, fascism might have lasted longer, communism might as well, and lord knows the ‘west’ was not what we would see as freedom loving and inclusive.