Deterrence, Norms, and the Uncomfortable Realities of a New Nuclear Age


One of the most important events of the last century was one that never took place — that is, thermonuclear war. Following the U.S. nuclear strikes against Japan in 1945, further use of nuclear weapons seemed inevitable. The United States and the Soviet Union amassed arsenals of unprecedented power, and competed for nuclear superiority in a contest that seemed certain to end in all-out nuclear conflict. But instead, neither utilized their arsenals, competition drove the Soviet Union bankrupt, and the Soviet empire collapsed. The United States and its allies dominated global politics after the Cold War, and democracy spread further across the world than at any other time in history. The Cold War ended without the use of a single nuclear weapon.

However, the non-use of nuclear weapons since 1945 can be misunderstood, and the wrong lessons can be learned. It is sometimes assumed that the absence of nuclear war since World War II proves that nuclear weapons are not relevant for national security, will never be used in conflict, or that a taboo against nuclear weapons will deter their use in the future. This thinking is dangerous, and may bring about the very event it assumes can never occur.



Nuclear weapons were never used during the Cold War because national leaders, even in situations like the Cuban Missile Crisis, judged that there was never any clear advantage in launching a nuclear strike. The risks never outweighed the perceived benefits, as a nuclear attack would clearly lead to nuclear retaliation. Deterrence worked during the Cold War, but only because Washington and Moscow worked hard to convince the other that using nuclear weapons would never be worth it. With the possibility of a new Nuclear Posture Review in 2021, it is important that policymakers study what will drive countries to use, or not use, nuclear weapons in the future.

The Nuclear Taboo Exists, But it Can Be Broken

It is sometimes argued that a normative basis of restraint, a “nuclear taboo,” is responsible for the lack of inter-state nuclear conflict. While such a taboo almost certainly exists, it is unlikely to prevent states from using nuclear weapons on its own. The decision to use nuclear weapons, like the decision to engage in conflict in general, has had a lot less to do with morality and a lot more to do with assessments of the national interest and domestic political considerations.

The United States and the Soviet Union refrained from nuclear strikes during the Cuban Missile Crisis due to mutual vulnerabilities. The crisis only de-escalated when both sides gave each other strategic victories — the Soviets removed its nuclear missiles from Cuba, while the United States removed missiles from Turkey. U.S. government officials decided not to use nuclear weapons during the Vietnam War because the nature of the conflict made them impractical and not worth the cost. Military analysts calculated it would take around 3,000 nuclear weapons a year to accomplish their goals in Operation Rolling Thunder. Following the Korean War, policies were put in place to immediately respond with nuclear weapons if a return to hostilities occurred. Nuclear weapons were used in Japan in World War II because of this same calculus. The U.S. government calculated it could save 500,000 allied lives and massive amounts of time and money by using them.

This is not to say the nuclear taboo has no effect on policy. The fear of the moral, reputational, and political costs associated with using nuclear weapons — specifically, using nuclear weapons first in a crisis — has certainly acted as a deterrent. The taboo, combined with the mindset that the weapons would not be necessary for victory, contributed to President Harry Truman’s decision to not use nuclear weapons in the early days of the Korean War, and prevented Gen. Douglas MacArthur’s original war plans — which included the use of up to fifty nuclear weapons and a belt of radioactive cobalt to prevent reinforcements — from being implemented. Even Secretary of Defense Robert McNamara is reported to have privately advised against waging nuclear war under any circumstances.

Arms control agreements, for their part, have reinforced the nuclear taboo by seeking to control potential escalation, provide transparency, and minimize the situations where it would be advantageous to use nuclear weapons. However, arms control agreements are not signed primarily for normative reasons. Countries — specifically Russia and the United States — have pursued arms control agreements as a means of furthering competition and offsetting an adversary’s advantages in specific sectors.

These agreements were pursued when there was a disparity in capabilities to curb competition and abandoned when the strategic conditions for the agreements were no longer favorable. For example, the Anti-Ballistic Missile treaty limited both the Soviet Union and the United States to maintain comparable capabilities and avoid a costly arms race. But Washington withdrew from the treaty in 2001 when it had a clear advantage in developing missile defense technology. The Intermediate-Range Nuclear Forces treaty, signed in 1987, allowed both sides to reduce tensions in the European theater, while strategically allowing continued competition in the realm of air and sea-launched missiles where the United States had a clear advantage. Russia began violating the treaty decades later when the strategic calculus changed, in the face of a proliferating Chinese intermediate-range missile force.

Thinking Through Deterrence

Nuclear deterrence is often assumed to work automatically, but in practice, nuclear states are inherently difficult to deter. Deterrence is not a condition achieved from simply possessing nuclear weapons; it is based on the perception of military power in general. Nuclear weapons drastically enhance a state’s strength by creating the capacity to cause catastrophic amounts of damage in a very short period of time, with strikes that are largely indefensible. Due to the unique characteristics of nuclear weapons, nuclear states become less likely to engage in conflict with each other. However, this makes it even harder to deter a nuclear state from campaigns against non-nuclear states.

The United States has extended its deterrence commitments to its allies in Asia and Europe. Unfortunately, this may be an empty promise. In the case of a crisis with a nuclear state like Russia or China, the potential for escalation to the nuclear level always exists. This begs the question: How far is Washington really willing to go to defend an ally, and how would the American people respond to risking nuclear war to defend an ally when there is no threat to the U.S. homeland?

If a nuclear power decided to use nuclear weapons against a state within the American nuclear umbrella (e.g., Australia, Japan, South Korea, and NATO allies, among others), the United States might refrain from responding with nuclear weapons, since doing so would risk its own survival. This dynamic is one of the reasons that the United States maintains a strong military presence and forward-deployed nuclear weapons in the territory of its European allies: The United States is far more likely to respond to aggression if American citizens are killed. This vulnerability allows states to build “theories of victory” that involve the use of nuclear weapons at the tactical level to offset conventional inferiority and deter foreign involvement.

Theories of Nuclear Victory

Nuclear use may be more plausible than many would like to believe. America’s adversaries invest a lot of resources in nuclear weapons, and a considerable amount of time thinking about situations in which they would use nuclear weapons and how to fight the United States under nuclear conditions. For example, if China decided to militarily retake Taiwan — a primary goal of the People’s Liberation Army — it faces two considerable obstacles. While it is possible it could succeed in an amphibious landing and take Taipei, the costs would be immense. Additionally, an invasion risks U.S. intervention and the outbreak of a war between the United States and China over the sovereignty of Taiwan. One of the goals of Chinese war planning against Taiwan is to ensure a quick and decisive occupation that would deter the United States from getting involved in the first place. Though China’s stated nuclear weapons posture claims a no first-use policy, this could be a situation where the cost-benefit ratio of using nuclear weapons is too good to easily overlook. The use of low-yield nuclear weapons against specific targets, such as Taiwanese military bases or coastal defenses, would have two effects. It would clear the way for a Chinese occupation with possibly fewer costs than a conventional approach, and would likely deter U.S. intervention. With no U.S. forces being harmed and China having demonstrated a willingness to escalate to the nuclear level, the United States is unlikely to find it worth the risk to intervene.

China would face economic and diplomatic costs from the international community, but it would face significant costs from annexing Taiwan anyway. Beijing could judge that using nuclear weapons would be worth it. Analysts have to honestly assess how much using nuclear weapons would improve Beijing’s chances of success, and weigh that against the repercussions of doing so.

Russia, with its aggressive nuclear posture, massive arsenal, and recent expansionist actions in Ukraine is another alarming case. Moscow’s calculated use of escalation controls shows a willingness and ability to calculate the appropriate use of force. If Russia can annex territory in Ukraine, it can conceivably do the same in the Baltics. A 2016 RAND study argued that Russian forces can rapidly move through and capture one or all of the Baltic states quicker than NATO would be able to effectively respond. Additionally, the Russian territory of Kaliningrad and its anti-access/area-denial capabilities provide an effective means of defending against NATO intervention. Countering such an offensive would almost certainly require strikes against Russian territory, which could trigger a nuclear response from Moscow. Russia is well practiced in utilizing the fear of further escalation and uncertainty to its advantage; limited nuclear strikes, or a nuclear demonstration in key areas, could be used to create uncertainty and fear of conflict escalating to a larger scale, deterring conflict at a lower level of escalation. If push came to shove, would NATO be willing to risk nuclear conflict for a small state in Russia’s backyard?

Of course, nuclear deterrence is most credible as a means to prevent foreign invasion. This has been the primary reason numerous states have sought nuclear weapons in the first place, including India, Pakistan, Israel, and even North Korea. A significant threat to the homeland of a nuclear state could lead to the use of nuclear weapons to make up for conventional inferiority, especially if the state is losing ground to advancing forces. The state may utilize a limited strike against an invader’s military bases, to cut off supply trains, or even against an adversary’s cities to coerce them into backing down. Furthermore, if the state feels its nuclear deterrent is being threatened, it may escalate by using its nuclear weapons under fear of a “use it or lose it” situation. Theoretically, this dilemma prevents invasion from occurring in the first place. But, if an adversary truly believes in this normative restraint and invades despite this deterrent, is it really believable that the state will continue to refrain from using nuclear weapons when its survival is at stake?

In the Cold War, analysts learned that it was very difficult to credibly engage and win in strategic-level warfare against a nuclear state. But this same lesson does not apply to nuclear versus non-nuclear states. The United States and Russia are unlikely to target each other in nuclear conflict — it is too risky. But nuclear weapons can be used against a non-nuclear state — outside of a nuclear adversary’s homeland — without triggering a suicidal response. There is a major difference between striking a nuclear power’s cities and threatening their survival and using low-yield weapons against a state that cannot retaliate at the nuclear level.

A counterargument is that it would not be necessary to use nuclear weapons against a non-nuclear state. However, this assumption may not always hold true, and the fear of inter-state nuclear conflict may be the edge a nuclear state needs to deter against foreign interference. If an American adversary uses nuclear weapons — in a manner that does not threaten the United States — will America blink? Is the United States truly willing to respond with nuclear weapons when doing so could quickly turn a situation that did not originally threaten it into one of mutual suicide?

Nuclear Restraint Is Not Based on Morality

Nuclear weapons may have increased deterrence between nuclear-armed states, but it is increasingly difficult to deter them in other campaigns. There are situations when a state may be able to use nuclear weapons to their advantage, and deterring against this requires hard work.

Nuclear weapons have not been used in combat in 75 years. Considerations of nuclear warfare have become taboo, which has contributed, in part, to the non-use of nuclear weapons for so long. But the taboo does not guarantee that nuclear weapons will not be used in the future, and history shows us that taboos are often broken. Recent evidence suggests that the nuclear taboo may not be as robust as many assume. An increasing number of Americans have even declared they would support using nuclear weapons to save American lives — a sentiment unlikely to be unique to the United States. In one study, 59 percent of respondents stated that they would support the use of nuclear weapons against Iran to save U.S. soldiers, and a different study showed that 77.2 percent would support a nuclear strike against al-Qaeda if nuclear weapons were deemed twice as effective as conventional weapons.

Unfortunately, the use of nuclear weapons may be increasingly plausible in the years ahead. The Joint Comprehensive Plan of Action, or “Iran deal,” meant to slow the inevitable proliferation of nuclear weapons in the Middle East, but was undermined when the United States withdrew from it in 2018. North Korean nuclear weapons and ballistic missiles have proven to be an effective means of deterring U.S. intervention and will not go away anytime soon, bringing fears of proliferation both in East Asia and to other dictatorships around the world. Bilateral arms control agreements are becoming less relevant as they weaken signatories against states outside of the agreement, and multilateral arms control agreements have become less likely to have meaningful content due to the wide variety of conflicting capabilities, arsenal sizes, and security concerns. The unfortunate reality is that the nuclear taboo is falling apart. If we wish to continue to see a world where nuclear weapons are not used, deterrent postures must be based on the assumption that states will use these weapons when it is in their interest to do so.



Gerald C. Brown (@GeraldC_Brown) is an analyst with Valiant Integrated Services, where he supports the Department of Defense nuclear enterprise and conducts nuclear strategy research and exercise analysis. Previously, he spent six years in the U. S. Air Force, Global Strike Command, working in nuclear security operations. All views expressed here are his own.

CORRECTION: An earlier version of this article stated that Dwight Eisenhower was president in the early days of the Korean War. That was incorrect. Harry Truman was president at the start of the Korean War.

Image: U.S. Air Force (Photo by Staff Sgt. Melanie A. Bulow-Gonterman)