Preemptive warfare is the practice of attempting to avoid an enemy's seemingly imminent attack by taking military action against them first. It is undertaken in self-defense. Preemptive war is often confused with preventive war, which is an attack launched to defeat a potential opponent and is an act of aggression. Preemptive war is thought to be justified and honorable, while preventive war violates international law. In the real world, the distinction between the two is highly contested.

In First Strike, Matthew J. Flynn examines case studies of...