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Mechanisms and Functions of Nuclear Deterrence: Historical Development of US Nuclear Strategic Theory

Masashi Murano

The Emergence and Development of the Concept of Deterrence

The idea of deterrence as such has an extremely long history. In his History of the War, which is known for its account of the Peloponnesian War, the oldest recorded war in human history, Thucydides recounts how Athenian leaders mobilized their troops and deployed their fleets to make the opponents reconsider launching attacks and thereby prevent hostile attacks. Of course, the Grecian idea of deterrence was not sufficiently systemic to be called a theory but was a practical habit adopted by Greeks to check adversaries' actions harmful to their interests.

The concept of deterrence became increasingly systematized with the end of World War II and the advent of nuclear weapons. Generally speaking, in many cases, "deterrence means discouraging the enemy from taking military action by posing for him a prospect of cost and risk overweighing his prospective gain." 1 Three conditions are prerequisites for deterrence to work: (1) a party's capability to impose an intolerable cost on its opponent, (2) the party's intention to use their capability, and (3) mutual recognition of the gravity of the situation both the party and its opponent face.

In the theorizing process, the concept of deterrence fell into the distinct concepts of "punitive deterrence" and "denial deterrence" based on differences in modalities. Punitive deterrence is an attempt to deter an opponent by showcasing the readiness to inflict an intolerable blow in retaliation for its action. As far as deterrence by military force is concerned, an asset ensuring this punitive deterrence is strategic nuclear forces represented by ICBMs that can reach the opponent's urban areas and inflict large-scale damage.

However, if the threat of retaliation falls short of deterring the opponent's hostile action, the capability to deny its action by force will become necessary. This type of deterrence is called "denial deterrence," a counter-concept of punitive deterrence. In the early stages of the Cold War, conventional forces deployed on the European front were the primary means of implementing denial deterrence. Yet, as the US nuclear strategy evolved, non-strategic nuclear weapons (tactical nuclear weapons) to attack enemy military targets and active defense capabilities like missile defense were also introduced. In addition to these, passive defense capabilities to limit nuclear strike damage by the installation of nuclear shelters and evacuation measures are also discussed as an element of denial deterrence.

Debates over the US nuclear strategy have swung back and forth about how to define the roles of punitive deterrence and denial deterrence. The remainder of this article is an overview of major debates on the US nuclear strategy from the Eisenhower administration through the Biden administration.

The Emergence of Massive Retaliation Strategy and Its Criticism

In 1946, military strategist Bernard Brodie first proposed the idea of "nuclear deterrence." He coined the word "absolute weapon" in the sense that it must never be used for military purposes to name nuclear weapons endowed with overwhelming destructive power not found in conventional weapons. He argued that the role of nukes should be limited to deterrence as such. 2 At that time, the United States, economically exhausted in the wake of World War II, had to establish, financially constrained as it was, a deterrent posture against the Soviet Union. Such a strategic imperative became even more urgent as war expenditures mushroomed as the country became involved in the Korean War that began in 1950. With this as background, Secretary of State John Foster Dulles launched the "Massive Retaliation Strategy" in 1954, which was the idea of deterring any Soviet military action by declaring large-scale retaliatory attacks with nuclear weapons against Soviet urban areas in retaliation for the numerically superior Soviet forces' potential invasion of Europe.

The Massive Retaliation Strategy, aimed at compensating for the lack of denial capabilities (conventional forces) with the punitive capabilities of nuclear weapons, appeared to be a cost-effective deterrent posture, but it soon encountered many problems.

The first problem arose when the prospect of maintaining a temporary comparative advantage in nuclear weapons and delivery means over the Soviet Union vanished sooner than expected due to the Soviet advancement. The "Sputnik Shock" or the "Missile Gap" demonstrated that Soviet ICBM technology, which had been underrated at that time, was superior to that of the United States.

The second is a capability-rigidity paradox. While the Massive Retaliation Strategy set a high initial threshold for escalation by depending on the powerful punitive deterrence of nuclear weapons, it envisaged no other option than retaliating with strategic nuclear weapons if that threshold had been overcome (deterrence failed). This is because proponents of Brodie-style nuclear deterrence implicitly assumed that the nuclear threat could deter all subsequent conflicts.

If deterrence by massive retaliation were to fail, the United States would be obliged to choose between "surrender or all-out nuclear war." The solution to this "nuclear stalemate" was the limited nuclear war theory that advocates carrying out limited nuclear war while maintaining superiority over the Soviet Union. Robert Osgood, the foremost proponent of the limited nuclear war theory in his time, began his argument by searching for a way to use military power as a rational tool in foreign policy. This is a direct refutation of the Brodie-style nuclear deterrence theory, which argues that the nuclear age made it more difficult for war to be "an extension of politics by other means." 3

According to Osgood, the rational use of military power requires a strategy of the kind that helps deter large-scale aggression that could lead to total war; deter or defeat small-scale aggression that falls short of total war. Four concrete measures to prevent a limited war from developing into an all-out war include: (1) setting limits on political objectives, (2) setting limits on military means, (3) setting geographical limits on the area of engagement, and (4) limiting weapons targets.

Henry Kissinger further developed the limited nuclear war theory. Kissinger followed Osgood's footsteps and added to his discussion the following minimum conditions for limiting war: (1) the two parties concerned should recognize each other's sanctuary exempt from attack, leaving the enemy's retaliatory capability intact; (2) instead of launching a series of successive attacks, the two parties should seek for political talks whenever war reaches a new stage and pursue military operations step by step; and (3) their aims should not be to defeat the enemy but to affect its will to carry out war.

Efforts were made by some strategists to reassess the effectiveness of damage limitation and denial deterrence as a solution to the "nuclear stalemate." For example, Albert Wohlstetter, who worked at the RAND Corporation linked closely to the US Air Force, conducted research on the forward deployment of bombers critical to retaliation. His analysis revealed the vulnerability of bombers to a Soviet first strike. He urged the military leadership to build out strike and defense capabilities to win a nuclear war.

Kissinger and Wohlstetter's arguments were focused primarily on the vulnerability of US security and strategic forces. Meanwhile, Englishman Anthony W. Buzzard also criticized mass retaliation but his discussion is unique in originating in concerns about the credibility of US extended deterrence. The Massive Retaliation Strategy concerned US allies not only whether it could deter a nuclear exchange between the United States and the Soviet Union but also whether it could deter limited wars that might break out in other regions than America or Russia. 4

With this awareness in mind, Buzzard argued that it would be impossible to contain a Soviet invasion of Europe with conventional forces alone, listing three scenarios as possible measures for the Western powers, including the United States and Britain, to take: (1) address a local invasion with the risk of all-out war in mind; (2) substantially increase conventional forces; and (3) defense by limited nuclear war. Buzzard concludes that limited nuclear war is the optimum defense strategy. However, he did not unconditionally support limited nuclear war. He emphasizes the importance of endeavors in the lead-up to limited nuclear war: arrangements that facilitate it for the Western camp to receive aid; maintaining superiority in tactical nuclear weapons at the disposal of land, sea, and air forces; and possessing a powerful strategic nuclear arsenal in the background. These arguments should be referred to in addressing the challenges the United States and Japan face today regarding extended deterrence.

Flexible Response Strategy and Assured Destruction Strategy

Debates critical of the Massive Retaliation Strategy affected new strategy development. The Kennedy administration, inaugurated in 1961, instructed Secretary of Defense Robert McNamara and General Maxwell Taylor, who was later to become Chairman of the Joint Chiefs of Staff, to undertake a thorough review of the Massive Retaliation Strategy. In 1962, the administration adopted a new nuclear policy guideline, the "Flexible Response Strategy," which admits that nuclear weapons alone do not generate deterrence and emphasizes establishing capabilities to wage war with military superiority under whatever condition. It dictates avoiding attacks on urban areas in the early stages of a conflict and prioritizing attacks on enemy military targets to avert rapid escalation. To tell the truth, this strategy heavily relies on the ideas of Wohlstetter and others as far as its emphasizing denial deterrence to exhaust Soviet forces swiftly, thereby limiting Western losses, or its aiming to conclude conflict at a stage short of all-out war (i.e., limited nuclear war).

The idea of the Flexible Response Strategy to control escalation with response measures addressing all levels of intensity is still today considered an ideal deterrence theory. However, when the Soviet Union's nuclear buildup began in earnest in the late 1960s, the situation became such that any attempt on the US side to acquire damage-limitation capabilities would easily be offset. In 1965, while maintaining the flexible response principle, McNamara announced the "Assured Destruction Strategy," which states that even if an enemy were ready to launch a first strike, the United States could deter hostile nuclear attacks on it and its allies by demonstrating a credible second strike capability that would ultimately inflict intolerable damage on the enemy.

Establishment of Mutually Assured Destruction and Rekindling of the Nuclear Strategy Debate

Nonetheless, the Soviet Union continued to expand its nuclear arsenal, and the United States and the Soviet Union were gradually forced to accept a situation of mutually assured destruction. As a result, from the 1970s onward, Americans saw a renewed debate over whether the United States and the Soviet Union should aim to maintain strategic stability based on mutual vulnerability or whether they should break away from the mutually assured destruction situation and aim for superiority in war-fighting capabilities. A symbolic ramification of this debate was the Strategic Defense Initiative (SDI) proposed by President Ronald Reagan in 1983, a grand vision of neutralizing Soviet nuclear missiles by linking space systems such as early warning satellites and laser satellites with ground-based interceptor systems—part of which underpins current ballistic missile defense technology. The SDI markedly reflected the strategy debate trend that pursued the possibility of winning a war by strengthening denial deterrence, rejecting to accept a mutually assured destruction situation. Yet, the United States' establishment of defense superiority could theoretically allow them to launch a preemptive attack without risking retaliation. This fear could lead the Soviet Union to launch a preemptive strike. Some criticized the SDI for potentially destabilizing strategic stability.

Although the majority of the plans envisioned for the SDI were not completed and not put into practical use before the disintegration of the Soviet Union, the American conservative community even today persistently believes that the Reagan administration's ambitious military expansion exhausted the Soviet Union and hastened the end of the Cold War. On the other hand, in the late 1980s, negotiations progressed on disarmament and arms control that attempted to improve transparency and strategic stability between the United States and the Soviet Union, leading to the creation of the first Strategic Arms Reduction Treaty (START). The US nuclear policy during the late-Cold War era is subject to varying interpretations.

The End of the Cold War and the Beginning of "Nuclear Oblivion"

Although the end of the Cold War brought a relative decline in the importance of nuclear strategy in US national defense policy, the US homeland did not become free from threat. During the review of threat perceptions in the 1990s and 2000s, there was increased vigilance against "rogue states" such as Iraq and North Korea, which were feared to possess or proliferate weapons of mass destruction, as well as terror and other asymmetric threats in the wake of the terrorist attacks of September 11, 2001. This led to a reassessment of non-nuclear strike capabilities that can be used for disarming attacks and denial deterrence like missile defense, as means of dealing with threats for which punitive deterrence is ineffective. The 2002 "Nuclear Posture Review (NPR)" of the George W. Bush administration demonstrated this trend. The document identified the "new nuclear triad" to sustain a comprehensive deterrence posture: (1) flexible strike capabilities including conventional weapons on top of the previous "nuclear triad" (ICBMs, SLBMs, strategic bombers); (2) defense capabilities such as missile defense; and (3) supportive technological infrastructure capable of immediate response. The 2002 NPR constituted the backbone of the Bush doctrine that did not dismiss preemptive attacks.

In his 2009 Prague speech, which contributed to his winning the Nobel Peace Prize, Barack Obama, first in his capacity as US president, expressed his dedication to realizing a nuclear-free world. He promoted disarmament and arms control initiatives, including the New START, a step to reduce the role of nuclear weapons in national security. President Obama's personal inclinations are discernible in the 2010 NPR, which positioned the prevention of nuclear terrorism and proliferation at the top of the nuclear agenda and articulated in terms of force structure that the nuclear-armed version of the Tomahawk Land-Attack Cruise Missile (TLAM-N) would be retired and its redeployment option abandoned. Regarding strategic stability, the document stated that the United States would liberate itself from the narrow interpretation predicated on mutual vulnerability that was in vogue during the Cold War and seek to achieve comprehensive strategic stability, placing a particular emphasis on strategic stability with Russia and China.

A Return to Great Power Competition and the End of "Nuclear Oblivion"

In the period from the late 2000s to around 2010, there was a latent positive assessment that relations between the United States and major powers over nuclear weapons would improve to a certain extent. However, various changes in the security environment that occurred during the eight years of the Obama administration—Russia's invasion of Crimea, the buildup of China's Anti-Access and Area Denial (A2/AD) capabilities through expanding missile forces, North Korea's development of nuclear weapons and ICBMs, etc.—disappointed Americans.

The 2018 NPR of the Donald Trump administration recognized that the focus of the nuclear issue had returned to the great power competition with Russia and China. The document expressed a sense of crisis about the two country's behavior: (1) violating or neglecting international arrangements; (2) increasing their strategic and non-strategic nuclear capabilities; (3) challenging—with increased nuclear capabilities as background—US conventional superiority through improving capabilities associated with space, cyber, and A2/AD and enlarging underground facilities; and (4) attempts to change the status quo and to challenge the international order by force. As concrete measures to counter these challenges, the Trump administration dismissed the "sole-purpose" nuclear policy considered by the Obama administration and, by introducing low-yield SLBMs, endeavored to achieve the flexibility to counter the escalation deterrence strategy.

The 2022 NPR released by the Joe Biden administration in October 2022 also contains various elements that indicate continuity with the nuclear policies of the previous administrations. (1) It reaffirms the need for the "nuclear triad," B61-12 nuclear bombs used in nuclear sharing with NATO, and their deployment spots. (2) It acknowledges that Russia and China are pursuing strategies using limited nuclear blackmail to achieve expansionist goals, pointing out that the United States should have the flexibility to adjust its deterrent to counter such strategies. (3) It pledges to allocate funds for the modernization of nuclear industrial infrastructure. (4) It does not adopt as its declared policy a "sole-purpose" approach that limits the role of US nuclear weapons to nuclear deterrence but recognizes the need to deter threats that could give a devastating blow to the United States and its allies by means other than nuclear weapons. (5) It reaffirms that the US nuclear strategy consistently pursues strikes against military targets and does not pursue a policy that intentionally targets civilians. (6) It declares largely continuing the nuclear modernization program initiated by the Obama administration and wholly taken over by the Trump administration.

Although these elements generally enjoy bipartisan support within the US strategic community, it is not sufficient to merely carry on the existing policy, without consideration of the dramatic change in the security environment where the United States is facing two nuclear superpowers, Russia and China, simultaneously for the first time in its history. The US strategic community has pointed out the following: (1) While referring to the possibility that the scale of China's nuclear capabilities could expand to become on par with that of the United States and Russia by the 2030s, the 2022 NPR goes no further than to say that "a near-simultaneous conflict with two nuclear-armed states would constitute an extreme circumstance," but fails to indicate the need or concrete means to practically deter China and Russia at the same time. (2) If China continues to expand its nuclear arsenal, the current US nuclear posture will not be able to deal with two fronts simultaneously, and the US government will be obliged to decide on a quantitative buildup of nuclear weapons. This is no longer a question of "whether to increase" but rather "when to start increasing." (3) The buildup of a nuclear arsenal, assuming a simultaneous response to China and Russia, will require more than simply reloading nuclear warheads, which had been unloaded following the New START, into surplus space on board missiles and bombers. It is necessary not only to reload old warheads currently in storage but also to expand the nuclear industrial infrastructure to design, produce, and deploy new warheads in the long term. (4) The 2022 NPR eliminated the phrase "hedge against an uncertain future" representing the long-standing, bipartisan-supported formal role of nuclear weapons. This policy change is logically inconsistent given that we are facing the most uncertain security environment in history. (5) The 2022 NPR declares the need to reduce the role of nuclear weapons, but the relevant definition is unclear, failing to explain how to accomplish what. (6) The document states that the current security environment does not favor the adoption of the "sole purpose" nuclear policy. But it does not deny the willingness to ultimately shift to the "sole purpose" nuclear policy. (7) The document gives a positive assessment of the W76-2 low-yield submarine-launched ballistic missile (SLBM) warhead, introduced by the Trump administration, for its role in deterring limited nuclear strikes. Contradictorily, however, it discusses potential alternatives to the W76-2. (8) The 2022 NPR decided to cancel the sea-launched nuclear cruise missile (SLCM-N) program that the Trump administration declared to introduce.

Implications for Japan

The above comments on the 2022 NPR are worth our attention in considering Japan's nuclear policy and the extended deterrence policies of the United States and Japan. The United States has consistently reduced its nuclear arsenal qualitatively and quantitatively since the end of the Cold War due to its overwhelming superiority in conventional forces. However, in the Indo-Pacific region, where the United States faces China, its superiority in conventional forces is no longer self-evident. In Europe and the Korean Peninsula, where the West continues to maintain its superiority in conventional forces, Russia and North Korea are increasing their dependence on nuclear weapons to compensate for their inferiority in conventional forces. Consequently, it will be essential for the United States to strengthen its nuclear deterrence capability to dispel the "nuclear specter" that those states are raising.

"G7 Leaders' Hiroshima Vision on Nuclear Disarmament at the G7 Hiroshima Summit," released on May 19, 2023, says, "The overall decline in global nuclear arsenals achieved since the end of the Cold War must continue and not be reversed." However, while Russia, China, and North Korea continue to expand their nuclear arsenals, it does not stand to reason that the United States must remain under the New START ceiling, still less that it must continue to be committed to unilateral nuclear disarmament, in light of the security environment facing the United States and Japan. Reducing the number and the roles of nuclear weapons means that at some point, the United States will be forced to abandon the principle it has maintained since the Flexible Response Strategy—the principle of prioritizing strikes on military objectives to avoid escalation. If its superiority in conventional forces is undermined and, as a result, it becomes incapacitated to pursue a strategy that prioritizes attack on military objectives, the United States will be ultimately forced to resort to retaliatory attacks on urban areas faster than its opponent, or to give up on retaliation and withdraw. This is a similar situation as when the Massive Retaliation Strategy was criticized years ago. Any policy that puts a country in a situation in which to choose a mass murder of innocent civilians or to give up vital national interests is hardly a morally correct one.

Sooner or later, the United States will decide to enhance quantitative nuclear capabilities. Japan should not wait for the United States to make a decision but should proactively consider what US nuclear posture and strategy align with its national security interests.

Masashi Murano is a research fellow at Hudson Institute in Washington.

(Translation by Tsutomu Inuzuka)

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