Preventive war occurs when a state launches a military conflict to prevent another state or other international actor from becoming a threat. This type of war differs from the more typical situation in which states go to war after a period of crisis or as a reaction to a particular event. Preventive wars are not in response to a specific crisis or direct threat to security, but rather to a perception of a potential change in the future balance of power between a state and its likely adversaries. Preventive war differs as well from preemptive war, in which a state attacks in order to disrupt an enemy about to attack first. The difference between prevention and preemption is often a blurred one, but preemption always occurs just before the outbreak of hostilities and is directed against an enemy clearly in the process of preparing an attack...