Traditionally, deterrence began with its forces and tools relying on conventional means of combat and the threat of using traditional weapons. This is illustrated by the Roman saying, “If you want peace, prepare for war.” The most common form of traditional deterrence is embodied in threats to inflict painful punitive strikes should an adversary commit aggression, a method known as deterrence through intimidation or fear of punishment. Traditional deterrence involves threats that utilize conventional weapons, while nuclear deterrence is limited to the threat of nuclear weapon use, whether that use is partial or total, limited or comprehensive. The importance of this concept arises from its pivotal role in understanding and interpreting the interactions of major powers, while simultaneously marginalizing medium and small states, along with various regional systems.
The Concept of Deterrence and Related Concepts:
There is no consensus among various literatures on a specific definition of deterrence, despite its long-standing existence as a phenomenon, political practice, and theory. Perhaps the most prominent definition is that it refers to the process of making a potential adversary understand that the price they will pay for hostile action far outweighs any gains they might achieve. Politically, deterrence is also defined as a calculated state aimed at either prompting the adversary to undertake a specific action or preventing them from doing so through threats of severe punishment, coercion, political blackmail, or conflict containment. It may also refer to a situation where one party considers an attack against the other, who is aware of this, and threatens severe consequences if the attack is initiated. Deterrence can also imply the absence of war between two countries or alliances; the absence of war means each party has successfully deterred the other, given that the military capabilities exist to compel the opponent to refrain from a specific military action.
In a related context, General André Beaufer defines it as “preventing an adversarial state from deciding to use its weapons—or, more broadly, preventing it from acting or responding to a specific situation by implementing a series of measures that present a sufficient threat.” The outcome sought through this threat (impact) is a psychological one. From this definition, it is clear that deterrence is employed as a policy and methodology within strategic operations. Despite the common acceptance of Beaufer’s definition, it limits deterrence to the military aspect or the use of armed force in order to achieve the desired influence, while according to both Paul Huth and Bruce, deterrence is an attempt by decision-makers in one state to compel decision-makers in another state to respond to their demands. This definition notably presents the option of conflict over cooperation through its indication of “coercion,” as it implies the existence of a party/parties with the actual ability to force others to act or refrain from acting.
Generally, deterrence relies on two fundamental pillars: one material and the other psychological; while the first involves securing all necessary capabilities and requirements for delivering punishment in an indisputable use of force, the second incorporates a psychological aspect aimed at instilling psychological impact on the adversary by convincing them of the utility of compliance with the deterring party. Otherwise, the adversary would face a punishment they cannot bear. Thus, deterrence involves a calculation or rational balancing comparing potential gains with losses incurred from engaging in an undesirable action.
Based on earlier meanings and definitions, it is important to note the multiplicity of concepts related to the idea of deterrence, such as cyber deterrence, which refers to preventing harmful actions against national assets in cyberspace and assets supporting space operations by any means. Indirect deterrence involves pressuring third parties that support terrorism rather than deterring the terrorists themselves. Denial deterrence aims to mitigate or reduce harm in the event of an attack and lessen the potential consequences of any terrorist assault. Punitive deterrence focuses on identifying high-value targets that lead more extreme leaders to weigh costs against potential benefits. Triadic integrated deterrence refers to a single state using threats and sanctions against another state to deter non-state actors from launching attacks from the territory of other states. Collective deterrence signifies the role played by international organizations, collective security systems, and NATO in deterring certain states from committing aggressive acts due to the fear of collective punishment. Mutual deterrence exists between nuclear powers like India and Pakistan, whereas assured mutual deterrence refers to each side’s capacity to destroy the other, even after undergoing a nuclear attack.
The Evolution of the Concept of Deterrence:
The underlying idea behind the balance of power system is the inevitability of conflict, which is driven not only by the relative national interests of states but is also fundamentally rooted in each state’s attempt to enhance its national power at the expense of others. Should one state achieve a decisive superiority in its capabilities, it threatens the independence and freedoms of other states, prompting the latter to resort to force in response to aggression. Deterrence was described during this phase as traditional, according to the type and nature of the weapons used, thus distinguishing it from nuclear deterrence, which is based on nuclear armaments. Therefore, deterrence under the traditional balance of power system was predicated upon the ability to achieve victory in war—should it be foreseen—by inflicting a crushing defeat on the enemy, vanquishing them, destroying their armies, and even occupying their territory, or at least imposing political will after militarily defeating them, if the adversary did not comply with the deterring party.
Accordingly, the fear of punishment—if the threats from the deterring party are ignored—relies largely on the assessment of the party capable of achieving victory in war. Thus, the threat of punishment—dependent on overcoming the enemy in warfare—serves to deter the opponent. Deterrence is achieved when the qualitative and quantitative differences of the factors that constitute the material and immaterial power held by either of the opposing parties translate into an effective capacity to exert successful influence or pressure behavior on the other side. Therefore, the value of deterrence, how it operates, and the conditions for its success all depend on those factors that enhance the military capacity of a given party, making the issue of war a losing proposition for the other, linked to the certainty of victory.
Certainly, the even distribution of power in the form of alliances and counter-alliances serves as a deterrent against the will of states wishing to wage war, as does the system of collective security aimed at supporting the common good of the global system and regional frameworks. This contrasts with traditional alliances, which manage security and peace through military force if necessary, with the ultimate goal being to prevent the actual use of military force.
Thus, one can argue that both the balance of power and collective security systems are fundamentally based on the idea of deterrence, forming one of the strong pillars of traditional deterrence strategy by preventing any state from utilizing its forces to disrupt the existing order, which can ensure security through countering aggression more effectively. This outcome aligns with the underlying assumption of the balance of power and collective security systems that form the basis of deterrence—that international behavior is constructed on elements of “rationality,” meaning the tendency to conduct continuous balances between the potential sides of risk and expected benefits. Therefore, if the risk assessments exceed the expected benefits, states will refrain from aggression.
In the context of the nuclear balance of power system, deterrence under nuclear weapons gained deeper meaning compared to that in the era of conventional weapons; this is indicated by the fact that traditional deterrence—despite the importance of its elements and components—did not prevent European powers from engaging in devastating wars. However, with the emergence of nuclear weapons, Europe has not witnessed wars among its main powers or superpowers (the Soviet Union and the United States) on a scale similar to past conflicts, despite the complexity and diversity of interests and the pressures imposed by certain ideologies rooted in the inevitability of conflict and the militaristic exclusion of others.
Despite all these factors, wars did not break out at the level of the two nuclear superpowers due to each recognizing the destructive nature of nuclear weapons. The consequences of a potential nuclear war—should it occur—would be comprehensive and mutual, negating the distinction between a victorious and a defeated party. This outcome imposed mutual constraints on nuclear powers, making the prospect of war an irrational choice. Consequently, the ongoing conflict among fighting parties can be resolved through peaceful and diplomatic means, eliminating the risks associated with nuclear weapons. In other words, nuclear deterrence revolves around nuclear threats based on mutual destruction of both conflict parties.
Initially, nuclear deterrence was based on concepts of power and threat, referring to each adversary’s capacity to completely destroy the other, alongside the principle of first-strike capability, meaning either the American or Soviet side’s ability to deliver a preemptive nuclear strike on their opponent, rendering them incapable of nuclear retaliation. To ensure the adversary’s incapacity to respond, the first strike was presumed to be devastating and comprehensive regarding all enemy nuclear weapons. Consequently, the attained deterrence became a product of mutual fear that either side might launch a devastating preemptive nuclear strike.
When an alternative strategic theory emerged based on the concept of second-strike capability, deterrence was represented in mutual nuclear deterrence—the capacity of both the American and Soviet sides to completely and utterly destroy each other in the event of a nuclear war between them, regardless of the initiating circumstances, due to their possessive retaliatory capability or second-strike ability. This critical truth rendered nuclear war a suicidal endeavor for both sides. Second, the most evident indicators of successful nuclear deterrence during the Cold War were avoiding the outbreak of comprehensive military conflicts due to assured mutual destruction—the serious threats of nuclear attack contributed to its avoidance. Moreover, deterrence fostered an environment of stability amid international crises and within the framework of international conflict between major powers. Alongside security and stability, nuclear deterrence also provided protection against both nuclear and conventional weapon attacks, although it did not prevent smaller-scale wars.
The nuclear strategy relied on the concept of “mutual nuclear deterrence,” thus creating a strategic situation known as “nuclear terror balance,” which was the central process governing the dynamics of international forces during the latter half of the 20th century. This denotes a “relationship in which states possess the capacity to launch a second retaliatory strike inflicting the initiating party with unbearable losses,” signifying a situation where no state can launch a devastating first strike. This system’s effectiveness derived from a critical fact: both superpowers succeeded in dramatically enhancing their nuclear capabilities to achieve second-strike destruction, after the essence of the strategy hinged on the principle of first-strike annihilation. That is, if the United States were subjected to a Soviet nuclear attack—regardless of its intensity and scope—it would still be capable of absorbing the shocks from the first strike and subsequently retorting with a massive retaliatory strike against the Soviet Union, targeting its industrial, civilian, and strategic centers.
Naturally, this situation declined following the “Star Wars Initiative” or “Strategic Defense Initiative” established by former U.S. President Ronald Reagan in March 1983 to use ground and space-based systems to protect the United States from anticipated attacks by strategic nuclear ballistic missiles. Consequently, the Strategic Defense Initiative was adopted in lieu of the strategy of assured mutual destruction. In response, the Soviet Union invested time and resources in developing a countermeasure to the Strategic Defense Initiative, termed the Soviet Strategic Defense, launching a new wave of arms race (1985-1991) leading to the dissolution of bipolarity.
The Concept of Deterrence in International Relations Theories:
The theory of deterrence finds its roots in realist thought and balance of power politics, and it played a significant role in managing security threats faced by states, receiving considerable attention during the Cold War as previously noted. Generally, theorizing deterrence—from a realist perspective—invokes several fundamental dimensions regarding the theory’s assumptions, conditions for deterrence, its requirements, types, and critiques directed at the theory. The deterrence theory rests on a series of assumptions about how potential adversaries understand and interpret the risks of retaliation. The primary assumption underpinning the theory is that an accurate understanding of international interactions will lead to a reluctance to undertake any increasingly dangerous or costly behaviors or actions. In other words, the rationality of an actor on one hand and the threat posed by this actor on the other deter any desired behavior to modify the current situation, particularly when the cost of such an action is evaluated against its expected returns. To yield this threat, it must rely on actual national capabilities that can convert this declared threat into a real one.
Alongside this assumption, the deterrence theory is built upon several premises, including—for example—the tendency of states with power to use it effectively—when the opportunity arises—against weaker states or in defense of their strategic interests, and conversely, a weaker or medium power state seeks to bolster its strength in response to this threat, derived from the rationality of the adversary, which hinges on calculating gains and losses to assess the outcomes anticipated from its actions. For deterrence to be realized in this sense, massive intelligence, military, and diplomatic capabilities must exist, along with the decision-maker’s precise knowledge of these capabilities, and an understanding of the factors influencing the decision-making process within their state and against their adversary.
However, these premises primarily focus on nation-states, their rationality, and military power, thus failing to explain how to deter non-state actors or cyber-attacks, for example. This has led some to propose the need to study the influence of the international context on actors’ behaviors and, consequently, their understanding of deterrence, indicating a necessity to attribute significant attention to cognitive factors. Some have attempted to intertwine deterrence with identity and with norms, positing that norms serve as frameworks enhancing the success of deterrence in achieving its objectives.
Overall, contributions from both constructivist and critical perspectives revolve around four key characteristics: the first is that deterrence can be learned; the success of a deterrent strategy hinges on actors’ perceptions. Accordingly, deterrence results from a “learning process,” where its effectiveness increases as understanding and practice deepen. The second characteristic is that deterrent practices are influenced by socialization processes; despite an actor’s awareness of the strategic balance with its adversary and its full comprehension of deterrence and its goals, it may decide for various reasons to resort to violence, as an actor’s experiences and accumulated knowledge impact its decisions. The third characteristic is that deterrence is affected by social structures, such as rationality, threat, and security. The fourth characteristic is that discourse shaping and defining actors’ knowledge and how they communicate in deterrence contexts cannot be ignored. The conclusion is that social context is formed through a learning process, and recognizing the significance of this context enables establishing a causal relationship between deterrence and violence avoidance. It also facilitates mitigating some internal contradictions in the theory, presenting a framework to understand how deterrence influences the behavior of both state and non-state actors and across broader issues than just military power.
The Effectiveness of Deterrence and Its Limits:
The effectiveness of deterrence depends on a set of conditions that can be summarized in the following points:
Capabilities: This refers to the tools and means prepared and ready to deliver the deterrence message, alongside the feasibility of their use and control with high efficiency to penetrate the enemy’s defenses. The critical factor determining the credibility and perception of capabilities is the resolve and ability to act at the right time and place, and that this action is capable of inflicting a degree of harm that puts the opponent’s mental state in a position to determine their level of response to this action, which can take various forms, the highest of which prevents the adversary from activating elements of action. This leads to altering the rules of engagement and transitioning them to less intense means.
Credibility: This condition represents the psychological dimension of the deterrent strategy and indicates the extent to which the deterrent can alert the adversary and convince them that the repercussions of their undesired actions could be severe. This hinges on two primary aspects: the ability of side (A) to clearly demonstrate the potential for heavy costs and the belief of side (B) in side (A). Generally, several factors influence deterrence credibility, including methods of war management, characteristics of the deterring state, the gap between the level of the threat to be deterred and the punishment the deterring state warns it could impose on the second party, the reputation of the threatened state, decision-maker nature, and more. Credibility depends on the nature of the threat as implicit or explicit, vague or clear, arising from a political center at the pinnacle of authority or from lower ranks; consequently, credibility relies on three core pillars: the ability to execute the threat, its nature, and the determination to make it a reality.
Rationality: This lies in each party’s recognition that war is an unethical and suicidal endeavor that must be avoided. To achieve this, the escalation of regional and international crises must remain within a defined threshold not to be surpassed; doing so indicates a descent into war and a breakdown of deterrence. For deterrence to succeed, it is assumed that the aggressor or attacker behaves rationally based on logical decision-making and sound evaluation; achieving this reality grants deterrence a degree of influence. However, if the attacking party operates under stronger psychological or emotional pressures than those considerations, it is certain that deterrence will not yield positive outcomes for the deterring state.
Information: Information is a fundamental prerequisite for success and enhanced effectiveness; secrecy cannot be perpetually maintained, and sufficient information must be allowed to pass to the adversary. If one side manages to augment its weaponry or modernize it while maintaining secrecy, that does not increase its deterrent capabilities.
Overall, deterrence requires a precondition for its effectiveness and its ability to achieve its objectives: to inform the adversary unambiguously about a definite intention to punish and retaliate should they fail to comply with what is sought from them or accept it, as well as to convey that the losses they would incur by risking a war would far exceed any potential gains they hope to achieve from it. This encapsulates the entire deterrent process. In general, the efficacy and utility of deterrence are among the major topics of contention; the leading questions in this regard are the diminished effectiveness of deterrence against terrorists and cyber-attacks due to the difficulty in identifying the attacker, alongside the escalating costs of mutual deterrence as it necessitates continuous updating and development of new weapons, accompanied by challenges in verifying the effectiveness of a particular strategy, especially regarding nuclear deterrence.
Deterrence does not prevent conventional wars; numerous cases exist where nuclear powers have engaged in conventional conflicts. For instance, the Falklands War between Argentina and Britain, China’s war against Korea, as well as the Viet Cong in Vietnam, and the United States’ conflicts with both Iraq and Afghanistan. Additionally, Arab states attacked Israel in the 1973 war, a period when the latter already possessed nuclear weapons, with numerous wars between India and Pakistan occurring despite both being nuclear powers. Furthermore, reliance on mutual nuclear deterrence leads to nuclear proliferation and arms races. This was clearly evident during the Cold War between the two superpowers, and it similarly applied at a regional level, as seen in the case of India and Pakistan. Deterrence can yield instability and lead to critical situations out of erroneous calculations, miscommunications, and technical mishaps. Moreover, deterrence can heighten animosity and distrust as adversaries repeatedly threaten each other. The failure of deterrence could result in the outbreak of a comprehensive nuclear war, as the failure of deterrence signifies a global catastrophe.
In conclusion, calls for revisiting the theory and re-adjusting its propositions according to changes in the international context and the multiplicity of unconventional threats, the expansion of nuclear proliferation, and a renewed interest in regional systems, which have previously been marginalized by the theory, have intensified. Consequently, the theory still requires more research and inquiry, while the foundation upon which deterrence was built remains unchanged. However, it is no longer feasible to limit definitions of deterrence solely to sovereign nation-states as the primary actors in international relations. Additionally, it is insufficient to condense definitions of deterrence into military force applications; it is more accurate to discuss the comprehensive nature of deterrence encompassing both hard and soft power. Military force is no longer the only means to achieve the desired effect on the deterred party.
