Deterrence Theory

Deterrence theory in international relations concerns the conditions under which a state i is able to prevent another state j from attacking i by convincing j that it runs the risk that this attack will be answered by a retaliatory strike that will inflict catastrophic damage. The theory has primarily been developed by U.S. strategic thinkers—most notably Bernard Brodie, Albert Wohlstetter, and Thomas Schelling—since the 1940s against the background of the nuclear arms race between the United States and the Soviet Union, which lasted until the end of the 1980s. Given this background, deterrence theory in international relations has particularly focused on the requirements and implications of a “stable balance of terror,” a situation, that is, in which each of the states involved has acquired the capability, in case it is the victim of a surprise attack, to launch a counterattack that will severely punish the aggressor.

Until the beginning of the 1930s, there existed only two ways to make sure by military means that an adversary refrained from armed aggression. One way meant that a state, with or without the assistance of allies, attempted to dissuade the opponent from attacking by building a defense strong enough to convince the opponent that it would not be worth its while to attack. The other way was aimed at compelling the adversary, again with or without the help of allies, to disarm. Thanks to a successful surprise attack on the adversary's territory (or by threatening to carry out such a preemptive strike), a state could compel its enemy to reduce its weapons arsenal or its military forces. Note that a credible defense means that the adversary is prevented from behaving in a certain way, though in the case of successful “compellence,” the adversary is forced to behave in a particular manner. For this reason, it is easier to prevent aggression through defense than through compellence. The preparations for war by the opponents were furthermore geared to fighting a war on the ground. Everything turned on the conquest of territory, or, conversely, on the prevention [Page 182]of the conquest of territory. The development of long-range bomber aircraft added a third method for preventing an adversary from attacking: deterrence. This means that a state threatens to punish its opponent in case of attack by “strategic bombardments” of the attacker's population and industries, rather than fighting it out on the ground. The aim of deterrence, just like defense, is to discourage a potential aggressor from attacking. Here, however, a state does so not by ensuring that the state's defense is so strong that it would never pay the aggressor to attack, but by seeing to it that an attack will be severely punished with the large-scale destruction of the aggressor's resources. Defense is a strategy based on denial, and deterrence is based on punishment. To explore the relationship between defense and deterrence still further, if a state succeeded in building a perfect defense, so that it was completely invulnerable to whatever offensive weapons a possible attacker might employ against it, then this state could no longer be deterred by any other state. The crucial chain in the theory's line of argument must be that a nuclear surprise attack will elicit a nuclear counterattack that will wreak havoc on the attacker's cities and population. As many have pointed out, it is highly problematic whether this will happen in fact. It may be rational to threaten with Armageddon to prevent an attack, but is it rational to carry out this threat when the deterrent has failed and the dreaded attack has started? Deterrence theory is apparently based on the assumption that the leader of a state that becomes the victim of a nuclear attack will act like an envious individual: that she or he will prefer the outcome that both states are destroyed to the outcome of defeat. But surely we can imagine that the leader who has to take the fatal decision to launch a retaliatory strike will not always be capable of willingly ordering the destruction of the lives of tens of millions of people out of revenge? A retaliatory nuclear strike therefore can never be a certainty, only a possibility. But if this is correct, then the credibility of the deterrent is undermined in advance and has thereby lost any effectiveness it might have had. Schelling recognized this problem and argued that the threat of inadvertent war and its consequent horrors—the suggestion that a disastrous all-out war can be the result of an accident, panic, or misapprehension, that there might be no time to reflect coolly on the fatal decision to launch the retaliatory strike—will lend the deterrent its credibility and convince the potential aggressor not to attack. In view of the possible terrible consequences, a “threat that leaves something to chance” will be credible, when in other circumstances it would fail.

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