Deterrence Theory

Deterrence theory gained increased prominence as a military strategy during the Cold War with regard to the use of nuclear weapons. It took on a unique connotation during this time as an inferior nuclear force, by virtue of its extreme destructive power, could deter a more powerful adversary, provided that this force could be protected against destruction by a surprise attack. Deterrence is a strategy intended to dissuade an adversary from taking an action not yet started or to prevent them from doing something that another state desires.

Military strategy and national security policy in which a full-scale use of nuclear weapons by two or more opposing sides would cause the complete annihilation of both the attacker and the defender
Military strategy and national security policy in which a full-scale use of nuclear weapons by two or more opposing sides would cause the complete annihilation of both the attacker and the defender 

Deterrence is an old practice, readily defined and described, widely employed but unevenly effective and of questionable reliability. Elevated to prominence after World War II and the arrival of nuclear weapons, deterrence became the central recourse for sustaining international and internal security and stability among and within states in an era of serious conflict. 

With regard to the presence of nuclear weapons in particular but also to deal with non-nuclear violent conflict, deterrence has been employed to prevent (or at least limit) the destruction of states, societies, and ultimately humanity. The greatest success has been that no nuclear weapons have been used for destructive purposes since the end of World War II in 1945. Deterrence has been widely used below the nuclear level but with very uneven results.

Deterrence has been intensively studied and tested as to its use in terms of strategy in international relations, the maintenance of stability in international relations, the conduct of violence and warfare in both international and domestic contexts, and in political affairs. Since deterrence is the use of threats to block or reduce the inflicting of serious harm, the existence of capacities for inflicting harm are readily maintained and periodically applied, so available deterrence capabilities provide a degree of continuing concern and a regular desire to at least do away with nuclear weapons and threats. A brief period in the ending of the Cold War saw a serious effort to reduce the reliance on deterrence, particularly nuclear deterrence, in international politics but it was soon replaced by serious movement in the opposite direction. Yet efforts to reduce the need for and use of deterrence continue.

Extensive efforts have been applied in the development of theories of deterrence, particularly to generate empirical theory in order to better understand and apply deterrence but without arriving at widely accepted results. This is the result of the considerable complexity of the subject, the activity involved, and the behavior of the practitioners.

The conduct of deterrence is now broader and deeper than before. It is under greater pressure due to technological, political, and cultural developments, and operates in a much more elaborate overall environment including space, cyberspace, and oceanic environs. Thus the goal of developing effective empirical theory on deterrence remains, at various levels, still incompletely attained. The same is true of mastering deterrence in practice. Nevertheless, deterrence remains important and fascinating.

Perfect deterrence theory and classical deterrence theory

Perfect deterrence theory and classical deterrence theory are two theoretical frameworks that have divergent empirical implications and dissimilar policy recommendations. In perfect deterrence theory, threat credibility plays a central role in the operation of both direct and extended deterrence relationships. But credible threats are neither necessary nor sufficient for deterrence to prevail, and under certain conditions, the presence of a credible threat may actually undermine deterrence. In perfect deterrence theory, the cost of conflict and status quo evaluations are also important strategic variables. Classical deterrence theorists tend to fixate on the former and ignore the latter. This theoretical oversight precludes a nuanced understanding of the dynamics of deterrence.

The Diversification of Deterrence

Deterrence theory is slowly beginning to emerge from a long sleep after the Cold War, and from its theoretical origins over half a century ago. New realities have led to a diversification of deterrence in practice, as well as to new avenues for its study and empirical analysis. Three major categories of changes in the international system—new actors, new means of warfare, and new contexts—have led to corresponding changes in the way that deterrence is theorized and studied. First, the field of deterrence has broadened to include non-state and nonnuclear actors, which has challenged scholars with new types of theories and tests. Second, cyber-threats, terrorism, and diverse nuclear force structures have led scholars to consider means in new ways. Third, the likelihood of an international crisis has shifted as a result of physical, economic, and normative changes in the costs of crisis, which had led scholars to more closely address the crisis context itself. The assumptions of classical deterrence are breaking down, in research as well as in reality. However, more work needs to be done in understanding these international changes and building successful deterrence policy. A better understanding of new modes of deterrence will aid policymakers in managing today’s threats and in preventing future deterrence failures, even as it prompts the so-called virtuous cycle of new theory and additional empirical testing.