Compellence

The ability to coerce another state into action, usually by threatening punishment. Scholars of international relations have traditionally focused on the compellent effects of force, but others have argued that the promise of reward is equally important. The economist Thomas Schelling coined the word compellence in his seminal 1966 book, Arms and Influence. Schelling described compellence as “a threat intended to make an adversary do something.” He distinguished this from deterrence, which is “a threat intended to keep him from starting something.”

Scholars have long argued about the most effective way to compel action. Schelling's work, though ground-breaking, is not without its critics. Schelling focused on the threat of escalating violence against civilian targets, but political scientist Robert Pape contends that compellence depends on making enemies feel that their military forces are vulnerable. Other scholars argue that carefully targeted economic sanctions can influence the behavior of other states. In these cases, nonmilitary tools of statecraft assist national security objectives.

Compellence and deterrence are both forms of coercion. Many scholars believe that it is more difficult to compel than to deter, although measurement issues make it difficult to be sure. First, deterrence is less provocative because the deterring state need only set the stage for action. It incurs little cost by making the threat. Indeed, costly actions are precisely what deterrence is supposed to prevent. Compellence, on the other hand, requires some form of costly action or a commitment to act. Second, the state that is the target of compellence may fear for its reputation if it complies with a threat. The targets of deterrent threats find it easier to “save face” because they do not have to act to comply. They can simply stay put and pretend that the deterrent threat had no impact on their behavior. Third, forcing states to act is difficult because states are large, complex bureaucracies. They move more slowly than individuals, and slowness may be confused with reluctance to comply.

There are two basic forms of compellence: diplomacy and demonstration. Diplomatic compellence involves verbal threats and promises. Shows of force also assist this kind of coercion; realist scholars note that most diplomacy is underwritten by the unspoken possibility of military action. Demonstrative compellence involves a limited use of force coupled with the threat of escalating violence to come if demands are not met. This kind of compellence is what Schelling referred to as the “diplomacy of violence.” A state does not unleash its full military potential; instead, it wages a limited campaign while instituting pauses to make the adversary consider the consequences if it does not comply.

Controversies over methodology and measurement plague studies of compellence. For example, it is sometimes difficult to tell the difference between demonstrative compellence and war. In addition, targets of compellence rarely acknowledge having been compelled; they don't want to admit that they responded to bullying. This makes it difficult to identify successful cases.

Some contemporary scholars argue that compellence involves more than threats alone. States may be afraid of punishment, but promises help to sweeten the rewards for cooperation. Moreover, compellence often requires some combination of threats and reassurances. Threats are more effective when target states are offered credible guarantees that they will avoid punishment if they comply. Without such reassurances, they have less incentive to cooperate with the demands of the compelling state. The appropriate balance of threats, promises, and reassurances depends on the character of the target state and the nature of the stakes.

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