I wrote Eve of Destruction hoping to get people to understand that the previous era of warfare—one in which there were at least some rules about when and why states could go to war—is over. It used to be, at least theoretically, that states would have to show some direct threat to their interests before they could go to war. They could act in self-defense, or in some way show a threat to themselves or their allies. Otherwise, they were considered aggressors. Usually, a state was considered justified in going to war if it could show that it was in danger and had no other choice. An entire body of thinking about “just war” was developed by Christian thinkers over the past millennium precisely to consider such questions and conditions.But now, with changes in technology, and new threats from enemies whose likes we’ve never seen before, like transnational terrorists, states are no longer waiting for actual threats to emerge. They are instead increasingly tempted to act against potential threats. This is called “preventive war” and until the twenty-first century, it was not considered either moral or wise. Bismarck called it “committing suicide out of a fear of death.”Of course, it was always acceptable to attack someone who was about to attack you. This is called “preemption,” and even today this is legal and justifiable in international law and practice. But the point of my book is that the difference between “preemption” and “prevention” has become very difficult to separate. We are in a whole new world of warfare; I believe states are going to be far more willing to use force than ever before.