The decision to use military force can be made in a variety of different situations and in response to numerous different triggers or actions taken by an enemy or adversary. A preemptive strike is a military action taken to forestall an imminent military attack or other type of threat. This type of activity is different from a preventive action, which is undertaken to counter a more distant threat. In this respect, a preemptive strike deals with a current threat, while preventive action deals with a potential or future threat.
Preemptive strikes are generally motivated by the fear of an impending attack or invasion. In this scenario, the leadership of a state believes its adversary is preparing for an attack or invasion. Instead of waiting for the attack to actually occur, the leadership decides to take action first— to launch a preemptive strike against the adversary.
The Israeli decision to strike against Egyptian forces on June 5, 1967, is an example of a preemptive strike. The Israelis believed that the Egyptians were poised for their own attack and that Israel could ill afford to absorb such an attack. As a result, the Israelis decided to launch a preemptive strike to forestall the imminent Egyptian attack.
A preventive action, on the other hand, would be undertaken to deal with a threat that could develop sometime in the future. With preventive action, the "threat" posed by the target is distant in nature, and in some cases a mere potentiality. The Israeli strike against the Iraqi nuclear reactor at Osiraq in June 1981 is an example of a preventive action. Israel struck the Iraqi facility in order to forestall the further development of the Iraqi nuclear program, which the Israelis viewed as a threat. This action was not really "preemptive" in nature, however, in that Iraq did not pose an imminent threat to Israel.
The distinctions between preemptive and preventive actions are important, but often confused. The 2002 National Security Strategy of the United States of America (NSS) describes a strategy identified as "preemptive," but in actuality it is closer to being preventive in nature. The NSS states, in the context of the threat from weapons of mass destruction, that "the greater the threat, the greater is the risk of inaction—and the more compelling the case for taking anticipatory action to defend ourselves, even if uncertainty remains as to the time and place of the enemy’s attack" (p. 15). The fact that the NSS stresses that the "time and place" of the attack are unknown makes the policy preventive. However, the NSS goes on to state, "To forestall or prevent such hostile acts by our adversaries, the United States will, if necessary, act preemptively" (p. 15). While the NSS does use the word prevent, it describes the policy as preemptive. Regardless of the terminology used to describe the policy, it fits squarely with the criteria of preventive actions. In this regard, the 2003 U.S.-led invasion of Iraq and ongoing conflict can be considered a preventive, but not preemptive, action—the threat faced was not imminent, but instead was of a more distant nature.
While preemptive strikes do involve the "first use of force," they are generally viewed to be reactive policies, or actions taken in self-defense. Preemptive strikes are usually carried out in response to some action taken by the enemy that is believed to signal preparations for an imminent attack. Preventive actions, on the other hand, are taken in response to activities that could develop into a specific threat at some point in time in the future.
This distinction has important implications, particularly with respect to international law. International law allows for the first-use of force in response to an imminent threat, but not in response to a distant threat. Or, in other words, preemption in response to an actual and imminent threat is OK, but preventive action is not. The line between imminent and distant threats, however, is becoming increasingly harder to distinguish in today’s world. With today’s modern technology, leaders no longer have the ability to see the adversary’s army massing at the border in preparation for an attack.
It is also important to realize that preemptive strikes and preventive actions are not a type of war, but rather should be viewed as a "pathway to war." In other words, a preemptive strike or a preventive action may signal the beginning of a war—but they are not in and of themselves distinct types of war. Any of the numerous types of war (e.g., limited war, total war, hegemonic war) can be started through the use of a preemptive strike or a preventive action. Furthermore, since preemptive strikes or preventive actions involve the first use of force, they can only be taken before the outbreak of armed hostilities. Since these actions are designed to forestall an enemy attack, once such an attack has occurred, the opportunity to take preemptive or preventive action has passed.
While there are numerous arguments as to why leaders would adopt preemptive or preventive strategies, the historical record indicates that states rarely employ these types of policies. One of the possible reasons why the leadership of a state would be hesitant to launch a preemptive strike is that there are substantial political "strings" attached to these actions. The state risks being labeled the aggressor in the conflict and potentially alienating allies and friends in the process—thereby jeopardizing support that might be essential during the rest of the conflict and in later relations. Additionally, there is a great deal of uncertainty inherent in any war or armed conflict. A leader would want to be quite certain that an attack was truly imminent before he or she struck the blow that would start the war process. But, this level of certainty is rarely present, and leaders are, therefore, reluctant to utilize preemptive strikes. This does not mean that leaders never decide to launch preemptive strikes, but rather helps explain why their use is much rarer than might be otherwise expected.
