By Gerald Brown
15-kiloton nuclear artillery shell fired from a 280mm cannon at the Nevada Proving Grounds on May 25, 1953 as part of Operation Upshot-Knothole.
“Nuclear weapons seem to be in almost everybody’s bad book, but the fact is that they are a powerful force for peace. Deterrence is most likely to hold when the costs and risks of going to war are unambiguously stark. The more horrible the prospect of war, the less likely war is. Deterrence is also more robust when conquest is more difficult. Potential aggressor states are given pause by the patent futility of attempts at expansion.”
John Mearsheimer, “Why We Will Soon Miss the Cold War,” The Atlantic, August 1990
Since the detonation of Little Boy and Fat Man ended the war in the Pacific, nuclear weapons have occupied an increasingly critical place in international politics. The weapons captured both awe and terror across the globe, sending policymakers and scholars scrambling to discover how to properly manage and exploit this new power. Through no small effort, the world has not only seen an era without the further use of these weapons in war but one without great power conflict—a precarious period of relative peace through deterrence.
However, to pretend that such peace was born automatically is folly. Such logic runs counter to humanity’s history of conflict and warfare. The current international landscape is changing greatly; as the world slides towards a multipolar world and return to great power politics, it must re-address the notion of nuclear conflict and deterrence in the modern world if peace is to be maintained. The use of nuclear weapons has become increasingly likely in the modern-era due to two primary reasons:
Nuclear multipolarity and state competition, resulting in an increasing number of competing, nuclear-armed states with historical tensions, leading to instances of escalation and the security dilemma between multiple actors.
Nuclear modernization and proliferation, including the development of low-yield, counterforce nuclear weapons that can be utilized without threatening a state’s survival in a limited nuclear conflict, particularly when parity is not present at all levels of nuclear escalation.
The possibility of escalation to a limited nuclear conflict at the tactical level, utilizing low-yield, counterforce nuclear weaponry is a plausible reality. Low-yield, counterforce nuclear weapons can be utilized in a limited fashion against an adversary’s military forces without threatening the survival of either state—particularly when there is a significant disparity between the nuclear capabilities of the states involved.
Mearsheimer states that within the social sciences, “those who venture to predict… should, therefore, proceed with humility, take care not to exhibit unwarranted confidence, and admit that hindsight is likely to reveal surprises and mistakes.”[1] Within political sciences, the sheer number of unpredictable variables makes any prediction anything but certain. It is, therefore, more prudent to analyze the changing landscape of the international nuclear system and identify the challenges and risks that threaten to upend the relative peace that has been maintained for the last 70 years. To preserve and enhance peace within the international system, it is critical to evaluate these potential risks in an unbiased manner while exploring all plausible possibilities. The scope of this piece is primarily limited to intentional inter-state nuclear conflict, and will not address threats such as accidental war, nuclear terrorism, or other related matters.
Competition Between Nuclear States
The structure of the international system has been one of conflict and anarchy for the entirety of human history. The world has never known an era without warfare; states compete to maximize their security and ensure their survival against one another. But in the modern era, this competition may have far more dire consequences. States now yield weapons with unimaginable destructive capabilities and are capable of delivering them at unprecedented speeds. While these weapons almost certainly cause states to act more cautiously, it does not undermine the competitive nature of international relations; states will still compete and seek primacy over one another, securing their own interests and security. While possessing nuclear weapons may raise the risk of failure and serve as a strong deterrent to other states, the weapons by themselves are not enough to prevent this competition between states. In some cases, they may go as far as to instigate it as states seek to ensure their security against another’s nuclear capabilities.
To properly evaluate this concept, a baseline in neorealist theory should be established. Neorealism holds five relevant truths. First, the international system is one of anarchy, with states as the primary actors, competing against each other without a higher ruling authority. Of these states, great power states are the most critical and relevant actors. Second, states will inherently possess some military capability to secure their power and security, a capability that can be both defensive and offensive. Third, a state can never be truly certain about another’s intentions; if a rival state is building troops or weaponry, one can never be certain whether it is intended to be offensive or defensive, despite what they may claim. Fourth, a state’s basic drive is for survival and sovereignty. Fifth, states are rational actors who seek to survive and ensure their security within this anarchic system.[2]
The primary difference between nuclear weapons and other weapons of war is not their destructive power, but the ability to inflict this damage at unprecedented speeds, and to inflict it against an adversaries’ homeland without having to first engage their military and defensive forces.[3] If a state utilizes its nuclear arsenal against an opponent’s cities, the opposing side’s conventional forces and defenses are irrelevant. A state can be losing a conflict and decide to destroy the opposition with a speed unprecedented in history by escalating to nuclear conflict, completely bypassing the military and defenses of the opposing state.[4] Hence, the basis of Mutually Assured Destruction (MAD) is one of mutual vulnerability, with both states accepting that the other could cause immense damage to their own at any time if they utilize nuclear weapons, and thus deciding to avoid it. This has been the backbone of nuclear weapons policy since World War II. The idea is that nuclear weapons ultimately mitigate conflict and escalate the cost of nuclear war to one that is far too high to pay, “war becomes less likely as the cost of war rises in relation to possible gains.” The fear of a retaliatory response deters the aggressor from initiating nuclear conflict in the first place. Wars occurring between nuclear states are likely to be limited in scale for fear of pushing one past the nuclear brink—if they occur at all. The cost of a miscalculation that leads to nuclear conflict is a far greater risk than the same miscalculation with a conventional army.[5]
However, the idea that actors would accept this vulnerability runs contrary to previous assertions made within the theory of neorealism. If it is accepted that states seek to preserve their sovereignty and security, parity seems to be an unlikely position for a state to find acceptable. The security dilemma highlights some of these challenges; when a rival state rises to the point where it can threaten another’s security, this state will bolster its own military strength and try to prevent any threat to its own security and sovereignty. Sometimes this may escalate into an arms race and ultimately into conflict.[6] In this instance, accepting that another state can eliminate your own with the press of a button fails to be acceptable. The very existence of these weapons is incredibly threatening to other states, and a state will act in whatever way necessary to mitigate that threat and ensure their own security. This concept has led to cases of nuclear proliferation in the past. For example, Pakistan built nuclear weapons in response to India’s nuclear test, and North Korea built nuclear weapons to ensure their regime’s survival and security against powers like the United States.[7]
Policymakers attempted to fix this problem during the Cold War with a secure second-strike capability. It was argued that if a state could still retaliate after suffering a fatal nuclear blow and deal the same fate to the aggressor, it would deter against preemptive strikes and force states to accept this mutual vulnerability and forego competition. As such, states sought to ensure their retaliatory capabilities through a combination of “hardening, concealment, and redundancy.”[8] Stationary weapons silos and shelters were hardened to improve survivability, submarine-based systems stayed concealed and mobile, and a massive number of nuclear weapons were produced and globally dispersed.[9]
However, this system was never truly accepted. If states had accepted this mutual vulnerability, the massive spending on modernization would fail to make sense. Even when these states claimed to accept MAD, their actions said otherwise. While the second-strike theory may have enhanced deterrence, it certainly did not stop states from competing to gain the nuclear edge over each other. Gavin asserts that even when quantitative parity was accepted between the two states, they still sought a qualitative edge over the other to secure nuclear primacy.[10]
The United States still pursued the ability to win a nuclear war with the USSR instead of accepting the status quo as expected and sought to be able to defeat the USSR’s second-strike capability. The U.S. engaged in programs to modernize its nuclear weapons, invest in missile defense technologies, nuclear submarine tracking, command and control technologies, as well as sought geopolitical advantage. Both states actively pursued the ability to outperform and outgun the other, to gain the edge and retain the capability to win a nuclear war.[11] The basic competition of realism did not change with the introduction of nuclear weapons. While states acted more cautiously, they still competed to secure their advantage and their security within the international system.
As time moves forward, the security imposed by this has become increasingly fragile. Even during the Cold War, the U.S. possessed a remarkable intelligence capability that would have been able to effectively find and target both stationary and mobile Soviet nuclear weapons. Long and Green authored an exquisite piece discussing now-declassified information that demonstrated our intelligence capabilities to track down enemy missiles with efficiency and precision via improvements in acoustics, ocean surveillance, and SIGINT (Signals Intelligence) technologies, capabilities that have significantly improved to this day.[12] Improvements in the targeting, accuracy, and reprogramming of weapons have further improved U.S. capabilities to destroy hardened targets. Elimination of fratricide from multiple strikes via these improvements has also allowed the U.S. to target and strike a hardened silo multiple times within a few seconds of each other. Lieber and Press claim that a strike against 200 Soviet silos utilizing two weapons per target in 1985 would have left approximately 42 silos still standing, while a similar strike today would destroy all 200.[13] Second-strike capabilities have become increasingly vulnerable in the modern age.
This isn’t to say that nuclear weapons have no deterrent effect—the lack of nuclear conflict during the Cold War certainly can stand testament to that. Instead, the point is that this deterrent is not as simple of a system as was thought, or perhaps wished; states will still compete, go to war, and may even engage in a nuclear conflict. The security dilemma was never truly mitigated and is still alive and well within the international system. But nuclear weapons can raise the cost associated with conflict and cause states to act more cautiously. Attempting to destroy a state’s entire second-strike capability is a major act and not one to be taken lightly. While a state may decide to attempt this if it was prudent to ensure its own security, it would certainly be an extreme situation in which few would likely be willing to bear. While states still engage in this strategic competition and attempt to gain the upper edge in a nuclear exchange, escalation to this level still seems incredibly unlikely due to the costs of failure.
Further, it is worth considering that the defending state may panic and retaliate upon the signal of the enemy launch, fearing for the security of its own second-strike capability. During the Cold War, policymakers steered away from these reactions, relying on the survivability of their second-strike systems to dissuade the benefits of preemption and secure deterrence. If faced with this situation in the modern era, knowing these systems may not be as secure as they once were, it would be difficult to judge what an actual reaction would be. This uncertainty may actually improve the traditional deterrence model, as states are fearful that their adversary will be pushed into a “use it or lose it” mentality. But this traditional view is primarily applied to a preemptive, large-scale strike against another state. Limited nuclear warfare may be a far more realistic scenario to consider. Limited nuclear warfare could be conducted in a manner that does not threaten a state’s immediate survival, and hence would not warrant an all-out nuclear response in retaliation. The concern of these attacks escalating to this level of large-scale nuclear conflict is a real one, but the initial use of a nuclear weapon at this limited level is a far more palatable option for governments to utilize.
Nuclear Proliferation and Multipolarity
Nuclear weapon use in a limited manner may be a serious threat, and the proliferation of nuclear weapons and the changing state of the world into a multipolar nuclear order may encourage this. Despite tensions between the U.S. and USSR, they were ultimately able to manage this competition in a bipolar nuclear world; this competition for advantage and security ended with the eventual collapse of the USSR. The security dilemma ran its course without the use of nuclear weapons, and the U.S. rose to become the hegemon of a unipolar world. However, in a multipolar nuclear world, the challenges faced previously are significantly exacerbated. Currently, the nine known nuclear-weapon states are the United States, the United Kingdom, Russia, China, France, Israel, Pakistan, India, and North Korea.[14] Strategies that worked in a bipolar world may not be as effective in the modern landscape, thus preventing the failure of deterrence—and the subsequent use of a nuclear weapon—may be more challenging than before.
The most recent nuclear state, North Korea, is one of the most troubling in the current group of nuclear states. North Korea is one of the world’s poorest states, facing harsh sanctions and isolation from much of the international community. Yet, despite the hardships, poverty, and poor economy of this autocratic state, it managed to defy the nonproliferation regime and create a fully operational nuclear arsenal.[15] Pyongyang is not bashful about its willingness to use its weaponry either, stating that it will use its weapons to “reduce the U.S. mainland to ashes and darkness.”[16] Such a clear security threat may increase proliferation elsewhere in response. Allison calls this the “nuclear cascade,” and suggests that if a state as weak and isolated as North Korea can defy the non-proliferation regime, other states are likely to follow suit.[17] If the United States is incapable of preventing such a clear security threat, why would Tokyo and Seoul rely on Washington to defend them in the face of a nuclear threat? Japan already has the capability to build nuclear weapons, possessing well-developed uranium enrichment and missile programs that could allow Japan to rapidly create a credible nuclear weapons program to defend itself and its national interests without the United States. According to The Council on Foreign Relations, there are thirty states that have the technological ability to quickly build nuclear weapons.[18]
While Pyongyang claims offensive intentions, it is incredibly unlikely to attempt to use its nuclear forces offensively against the United States. Doing so would be an act of suicide, the disparity between U.S. and North Korean forces is far too great. Instead, these weapons were more than likely obtained for defensive purposes. Pyongyang may not be able to destroy the United States, but it can ensure its own sovereignty. Forcibly trying to topple the Kim regime could escalate into the use of nuclear force if Pyongyang got desperate, and a strike designed to eradicate their nuclear weapons would again invoke this “use it or lose it” mentality. While Pyongyang may not be able to destroy the U.S. with its capabilities, it can undeniably cause immense harm to the US. It could cause even greater harm to smaller, closer countries such as U.S. allies Japan and South Korea. Knowledge of this is a strong deterrent against U.S. intervention, allowing Pyongyang to carry on less cautiously without fearing foreign intervention. The creation of this deterrent may have effectively ensured the sovereignty of the Kim regime for the time being, and they are unlikely to relinquish this guarantee. The establishment of this deterrent highlights some of the challenges in the modern nuclear era. North Korea’s outright defiance of the nonproliferation regime sends a signal that other states can build a nuclear capability as well and that such a force may be an effective way to guarantee their sovereignty against the Western world.[19]
Proliferation to autocratic states is a cause for concern, primarily because they are considerably less stable than democratic states and may be more willing to utilize a nuclear weapon. The inherently volatile nature of these regimes poses a significant challenge. North Korea has a very poor and impoverished populace, held under authoritarian rule. Regimes such as these are not known for their longevity and stability. The threat of regime change and revolt from within is a realistic consideration with autocratic states. If this occurred, it could result in the loss of a nuclear weapon, or their domestic use to quell a rebellion.[20] It could also escalate into conflict as Chinese and U.S. forces both seek to secure their nuclear assets and end up in conflict with each other. China would certainly not accept U.S. forces along the Yalu river, and both would want to immediately seek to ensure the stability of Pyongyang’s nuclear assets.
Autocratic states could also safely assume that Western powers would prefer it if they were a democratic government friendly to the West. With the international liberal orders push for global democracy, autocratic rulers are likely to fear Western interference. After Pyongyang’s recent success, a nuclear weapons capability may appear to be an effective way to prevent Western interference and ensure its sovereignty.
With smaller autocratic states, the constant external and internal threats to the stability of their regimes breed paranoia and volatility. Leading government officials tend to be promoted based on loyalty rather than competence, and disagreement or discontent with the dictator may be punished harshly, stifling progress and ingenuity. These regimes also tend to have strong military leadership directing the country. Pakistan is notable in this regard, where the military maintains significant control over the government and has a history of instigating a military coup when they dislike civilian leadership. Pakistan has had four separate military coups since its creation, with military dictators constantly consolidating their power into the executive branch.[21] Military leadership is far more likely to see nuclear weapons use as a viable option, which increases the instability of nuclear autocratic regimes even further. Civilian leadership has arguably been a key factor in preventing nuclear use thus far. Military officers often possess a different mindset and attitude on the subject than civilian leadership due to their career path. During the Cold War, there were numerous instances where the Joint Chiefs of Staff were far more willing to utilize nuclear weapons in a preventive war and were reined in by U.S. civilian leadership.[22]
Throughout the Cold War, there were numerous false alarms; equipment detected missile launches that did not exist, drills were confused for real launches, and communication cut-offs and the “fog of war” nearly led to nuclear use.[23] If faced with similar threats, it is less likely that an autocratic state will respond in such a level-headed manner. With shorter-range nuclear weapons, this could be exacerbated. These states are less likely to have a robust, survivable nuclear arsenal. If a state’s nuclear arsenal is threatened, it is likely to take action to ensure its survival or use. Without having the same geographic separation that the U.S. and USSR did, several states today rely on shorter-range weapons, like short-range missiles and multi-role fighter/bomber aircraft. Whether these weapons systems carry nuclear or conventional payloads may be unknown; being forced to make a rapid decision to respond to a potential threat may push a state over the edge to ensure its security.[24]
Particularly concerning, at least in regard to stability, is the smaller size and the heightened vulnerability of many arsenals compared to other states. The multipolar nuclear order lacks the same levels of parity both quantitatively and qualitatively that were present in the Cold War. The number of weapons between states varies significantly. While exact numbers are typically classified, experts have estimated a range varying from approximately 20 warheads in North Korea, to around 6,000 for both the U.S. and Russia.[25] Destroying all the nuclear weapons in North Korea is significantly easier to do than performing the same action against the U.S. or Russia, and this may be especially true with an even newer autocratic state that develops a brand-new nuclear capability. The parity dilemma further extends to conventional capabilities. A state with inferior conventional capabilities such as North Korea compared to the U.S. or Pakistan compared to India, may feel pressured into utilizing, or at least threatening, to use its nuclear capabilities to make up for its inferiority. If a nuclear-armed state lacks an effective conventional response option and is faced with a crisis that threatens its security, it may decide to escalate with a limited nuclear strike to preserve its integrity and security.
The primary barriers to the use of nuclear weapons in the Cold War were the second-strike capability and the threat of mutual destruction. But as has been discussed, this second-strike may not have been as effective as previously thought and is particularly less effective in the modern age. Such disparity between arsenal sizes eliminates many other concerns with a nuclear first strike. The chances of eliminating a second-strike capability are significantly higher in many circumstances, and the abolition of the Anti-Ballistic Missile (ABM) treaty has made the idea of intercepting any surviving nuclear weapons much more likely. While ballistic missile defense is a fickle and inconsistent technology, the prospect of defending against a few surviving second-strike weapons is much more realistic than trying to defend against a general nuclear war.[26] The disparity between military strength has led to conflict through all history, and this has not changed with nuclear weapons. If a state thinks it can successfully engage and win in a conflict that would bring great benefit and little harm to itself, the threat of this occurring is great. As Thucydides cited the Athenians telling the Melians during the Peloponnesian War, “the strong do what they can and the weak suffer what they must.”
Faced with this fact, the receiving state may very well utilize its weapons as discussed to prevent the loss of its second-strike. The knowledge of this possibility enhances deterrence, but with great disparity, it may not be enough. If the aggressor feels that it can effectively defend against such a limited strike, or that it would be able to conduct the strike prior to the launch of enemy weapons, it may decide to do so. The varying distances between states and shorter-range weapons that can be utilized in the modern era make a difference as well. Nuclear rivals like Pakistan and India can strike each other much quicker than the U.S. and USSR could strike each other in the Cold War. This gives even less reaction time to make such a large decision and increases the chance that a disabling first strike could be pulled off.
The security dilemma is notable to mention here as well; the U.S. and Russia currently enjoy a considerable nuclear advantage over all other states. But another state building their nuclear deterrent or conventional forces, and hence threatening another’s superiority as happenstance, is likely to escalate into an instance of the security dilemma. In a multipolar world, this is especially relevant. Competition between two states is much simpler to manage, but when reacting to one state, a state may create escalation between several states simultaneously.[27] The recent abolition of the Intermediate-Range Nuclear Forces (INF) treaty serves as a useful example. The U.S. and Russia found this to be an acceptable state for several years; however, China’s rising conventional and nuclear power, including the development of intermediate-range weapons, may have threatened this. Russia, considering China’s proximity and fearing for its own security, hence develops intermediate-range weapons of its own to match this threat, pushing the U.S. to respond in kind as well.
Bracken expands on this concept, explaining how decisions targeted towards one state could affect several, and the challenges this brings to nuclear strategy.[28] In his example, the U.S. deploys a precise conventional missile capability designed to penetrate and destroy North Korean and Iranian nuclear infrastructure on its submarines, a move being considered at the time Bracken wrote The Second Nuclear Age. However, this capability has been condemned by China, for fear that it will have the added effect of threatening their own nuclear deterrent. China responds to these deployments by remodeling its deterrent and deploys a more mobile nuclear force that is harder for the U.S. to track and destroy. In turn, this agitates India and threatens their security, so they decide to respond to the increased Chinese nuclear threat by improving their own nuclear forces.
Any development to India’s nuclear doctrine or weapons program will surely affect Pakistan, and will surely escalate the already strenuous tensions between the states. The result is a cascading, delicate dynamic that is significantly more complex than the comparatively simple bipolar relationship deterrence theory was founded under. The security dilemma and realist competition between states aren’t so easily managed in a multipolar world and may very well escalate out of control. When a proper second-strike capability is not always present or a nuclear strike is unlikely to threaten the survival of a state and will serve its interests, the threat of such acts occurring is heightened. The multipolar nature of the world and challenges presented by the fog of war may make nuclear escalation in a crisis significantly more likely.
Multipolar competition has become all too apparent in the modern-day. Both China and Russia have been increasing their military might and seeking to expand their influence, challenging U.S. hegemony. The return to great power politics makes the more precarious state of the multipolar nuclear order more dangerous. Some comfort can be taken in the notion that the ideas and strategies that deterred strategic nuclear warfare in the past are still in place. A strategic strike against a nuclear powers’ cities would be counterproductive and almost certainly result in likewise retaliation, an unacceptable consequence and a strong deterrent in the majority of situations. But this strategy does not prevent a state’s aggression and expansion elsewhere. While the U.S. may be committed to its strategy of extended deterrence, the bulk of its warfighting capability rests on its conventional power.
While it may claim otherwise, a nuclear strike against an ally under the U.S. nuclear umbrella by a great power state is unlikely to be met with nuclear force, lest this escalates into strategic nuclear warfare between the two nations. The United States is unlikely to engage in a strategic nuclear war with another state to defend an ally’s security unless U.S. national security and the U.S. homeland is directly threatened. What is more likely to prevent a state from using a strategic strike against non-nuclear adversaries’ cities is the lack of necessity. There are few situations in which this is useful, as most goals can be accomplished nearly as easily with conventional forces. They certainly exist, the nuclear use in Japan highlights this, but if a state has a conventional option that is nearly as effective it would likely take it. While a strategic strike against a nuclear-armed adversaries’ cities is still unlikely, there are two more realistic options that should be considered: a counterforce strike against an adversaries’ nuclear forces, or a counterforce strike against an adversaries’ conventional military forces.
Tactical Nuclear Conflict
Nuclear weapons cannot be lumped together in one class. The way they are used and the style of weapon are important distinctions. Reaching as far back as 1965, Kahn made these assertions in On Escalation, describing different levels of escalation in nuclear conflict instead of the presumed jump to all-out nuclear war. He asserted that nuclear conflict could be fought at a variety of different levels, escalating and de-escalating between them depending on the circumstances. One of the most important distinctions in the modern day is that of counterforce and countervalue weapons. Counterforce would be used at the tactical level, against a state’s conventional or nuclear military forces. Countervalue is what is thought of more traditionally in a nuclear conflict, a higher-yield attack used on the strategic level, against a state’s cities, industry, and personnel. The attacks against Hiroshima and Nagasaki were of this sort, strategic attacks designed to coerce the state of Japan into surrendering, knowing they could not retaliate.
The mushroom cloud of the Tsar Bomba hydrogen bomb.While the conditions and necessity for a state to conduct a strategic strike may still be unlikely, a more recent trend in nuclear weaponry may be a far more realistic and pressing threat. During the Cold War, states focused on creating the largest, most awe-inspiring and outright terrifying arsenals they could, and fielding the largest, deadliest weapons that they could create. The USSR went as far as to create and test the largest nuclear weapon ever to exist, the Tsar Bomba, a multi-stage hydrogen bomb with a yield of 50 megatons. For perspective, this weapon possessed approximately 1,570 times the explosive power of the nuclear weapons detonated in Hiroshima and Nagasaki combined.[29] Such a massive weapon is terrifying, but also altogether unnecessary, and was unlikely to be used. Much of what was produced in the Cold War was an unbelievable threat. Instead, the modern nuclear age may see more utility in moving the exact opposite direction, fielding low-yield, precision, tactical nuclear weapons.
One of the primary concerns with tactical nuclear weapons is they create a far more realistic threat, blurring the line between conventional and nuclear conflict.[30] Strategic nuclear weapons used against an opponent’s cities are unlikely to be used. At the minimum, this would invite great harm against each other’s respective states, certainly enough pain that one would seek to avoid it. Few gains are worth the risk of losing one’s major cities and infrastructure. Tactical, low-yield nuclear weapons may avert this obstacle, however. If these weapons are utilized against an adversaries’ conventional forces, and outside of an adversaries’ homeland, it is unlikely to cause massive nuclear retaliation; neither the aggressing nor defending states’ survival is ever threatened in this scenario. These weapons may have the added capability to target and destroy enemy forces and defenses more efficiently, more accurately, and without the heavy number of civilian casualties that may be present in a traditional nuclear strike. If a state can vastly improve its warfighting capability without the threat to its survival that higher-yield, strategic weapons created, it could be expected to take advantage of these weapons.[31]
The most likely threat for nuclear weapons use would be a state escalating to tactical nuclear use against an adversaries’ conventional forces, attempting to coerce them into backing down, ensure victory, or deter foreign intervention.[32] For example, if China decided to retake Taiwan, it may be able to do so conventionally, but such a crisis has the potential to incite an American military response in defense of Taipei and have considerable Chinese casualties. If U.S. forces responded, Beijing may believe tactical nuclear strikes against those forces would be an effective means of creating military superiority against a conventionally superior force and that low-yield weapons could be utilized without threatening China’s survival. Such a measure would be incredibly unlikely to incite a nuclear response against China’s homeland, for fear of a similar response.
In a different, albeit unlikely scenario, tactical nuclear strikes against Taiwanese defenses in an initial strike may have the added effect of deterring an American response in the first place, raising the threshold for American intervention. In this scenario, Beijing would be operating under the impression that the U.S. would be sent a message that coming to Taipei’s defense would not only mean great power war but nuclear conflict, as well. Without facing a threat to its own homeland, it would be far less likely to incur that risk. The use of a nuclear weapon against a non-nuclear weapons state will almost certainly not result in nuclear use against the aggressor.
Similar situations could be seen by attacking a military base outside of a state’s homeland. The idea of such a strike occurring outside of ones’ homeland, on forward-deployed forces is critical. Yield differences mean nothing if the attack is directed at a state’s homeland, directly threatening its security. Escalation to this point is almost certain to result in strategic level escalation. An adversary cannot accurately guess the yield level of an opposing weapon in flight. While lower yield weapons are more useful for tactical level warfare, the target is the more important distinction.
A state must be able to fight at both the tactical and strategic levels. If the aggressing state escalates to the tactical nuclear level, and the responding state is unable to respond at that level, it will be faced with two options: concede and yield or escalate to the strategic level. The latter of these creates a threat to their own security via reciprocation at the strategic level—and hence is an unlikely choice.[33] The possible exception to this would be if the aggressing state is unable to retaliate at the strategic level themselves. As such, a significant disparity between great power states at the tactical level may be a cause for concern. Strategic capabilities do not need to be vast to create an unacceptable level of harm to a state, all that’s needed to deter at the strategic level is a small, survivable arsenal. Certainly, a single nuclear strike on an American city is an unacceptable consequence, and it would take a very extreme situation for a state to be willing to risk that. Defending a foreign state such as Taiwan that will not impact the survivability of the United States is not such a situation.
If a significant disparity at the tactical nuclear level exists, a state may be able to prevent foreign intervention when engaging in expansive conflict. If China maintained a far superior tactical nuclear capability than the U.S., and even a minimal strategic second-strike capability as described, it is very likely that it could escalate to the tactical nuclear level in an attempt to force the U.S. to de-escalate. With the initial use of tactical nuclear weapons against Taiwanese defenses, it is possible it could prevent U.S. intervention altogether if its capabilities were vastly superior at the tactical level of escalation. Taiwan is certainly not the only example; wherever a significant tactical nuclear disparity exists and state aggression against non-nuclear states cannot be deterred, the U.S. policy of extended deterrence will not hold any merit. The same could be seen with any state’s expansion, such as Russia reclaiming the Baltics, or China moving to use force seize territory claimed by both India and itself. If a state can utilize tactical nuclear weapons and would benefit more than it would risk, there is a possibility of it doing so.
A U.S. Air Force F-35A Lightning II Joint Strike Fighter (Photo: U.S. Air Force Master Sgt. Donald R. Allen)Unfortunately, this is not a mere theoretical threat. The most recent Nuclear Posture Review identified significant expansion and modernization of Russian and Chinese nuclear forces, while the U.S. has expanded only incrementally. Since 2010, the F-35A multirole fighter jet is the only new nuclear delivery system produced by the U.S., whereas Russia has developed a combined total of 14 new delivery systems across the nuclear-triad and China has fielded nine new ground and sea-based delivery systems. The 2018 Nuclear Posture Review further mentioned Russia’s vast expansion of tactical weapons systems that can hold either a conventional or nuclear payload.[34] These types of weapons systems are not held accountable under the START treaty. As of 2016, the only weapon in the U.S. arsenal designed for non-strategic purposes was the B61 gravity bomb, an air-based tactical nuclear weapons system, of which the U.S. maintains an inventory of approximately 500. These weapons have a max payload of about 50 kilotons, which may still be far too high to effectively target conventional forces and provide an effective tactical-level deterrent.[35] The U.S. does not have tactical nuclear weapons on any other level of the nuclear-triad, a gap which the 2018 Nuclear Posture Review addressed and called to fix.[36] While the U.S. has slowed down its nuclear programs and the development of tactical nuclear weapons, other countries have not followed this lead, and instead have been exploiting it as a weakness. Retired Vice Admiral Robert Monroe claims that Russia is around 20 years ahead of the U.S. in terms of its low-yield nuclear weapons capabilities.[37]
Source: 2018 Nuclear Posture ReviewThere may be an upside though. Tactical nuclear weaponry, a far more believable threat, may be used to enhance deterrence if used properly.[38] Decisions to aggressively expand and enter into war are made by calculating that a state can win the encounter and the benefits outweighing the costs.[39] If Russia is to invade the Baltics, it must find that it has a high chance of success. Either it has the capability to defeat NATO defenses and responding forces via tactical nuclear conflict or be confident NATO will not come to their defense, whether this is from initial tactical-nuclear escalation or for other reasons. Strategic weaponry may work to deter a threat from an attack on a state’s homeland, but it remains too unbelievable of a threat to deter another nuclear state from expansion elsewhere. The proxy wars and conflicts against non-nuclear states since the end of World War II provide a solid historical precedent for this. Tactical nuclear weapons may be a more believable threat and be able to deter where strategic weapons could not. If the U.S. announces its commitment to defend Taipei and has an arsenal of tactical nuclear weapons at relative parity to China’s, then China is less likely to try to take Taiwan by force in the first place. The same goes for any other theoretical expansive military action taken by a nuclear state armed with a robust tactical nuclear capability.[40]
While the aggressing state’s survival is no longer threatened, the cost of war is heavily escalated and chances of success much lower. Tactical nuclear weapons will cause immense and swift destruction to conventional forces on both sides, a risk that is unlikely to be taken. With relative parity, these weapons greatly raise the threshold of military action and may make the risk of conflict even less prevalent if this parity is maintained amongst great powers. This is still not absolute, as even with tactical nuclear parity, the willingness to commit to such an act must be believable. The defense of another state without a direct impact on one’s own homeland may not be believable, and the aggressor may call the bluff. However, not knowing for sure and having the commitment of extended deterrence will cast enough doubt in the majority of situations, as the cost of being wrong would be immense. The best way to prevent such a threat from materializing is to credibly be prepared to fight at all levels if it does.[41] While this may not guarantee that these weapons will not be used and remain deterred, the lack of parity will almost certainly invite their use if it will give another state superiority over the United States. If a state can topple a stronger conventional force and achieve its goals with nuclear force, without threatening its survival, it will do so. With the competitive and fragile nature of a multipolar nuclear order, it will be of the utmost importance to be able to manage escalation at all levels of nuclear escalation.
Conclusion
In the modern nuclear age, the use of these weapons is increasingly likely, particularly if doing so will give a state a significant advantage over another. Deterrence has merit, but it undoubtedly lies in the presence of a realistic, credible threat, across all levels of the threat spectrum that mitigate this potential advantage. Nuclear multipolarity and increased interstate competition are resulting in an increasing number of competing, nuclear-armed states with historical tensions, leading to instances of escalation and the development of the security dilemma between multiple actors. Nuclear modernization and proliferation are prompting states to develop low-yield, counterforce nuclear weapons which can be utilized without threatening a state’s survival in a limited nuclear conflict—particularly when parity is not present at all levels of nuclear escalation.
Undeniably, the use of another nuclear weapon, either tactically or strategically, is a travesty that all states must try to avert. At the same time, the destructive power of these weapons does not fundamentally alter the landscape of relations between states. If this power is to be kept in check, this idea must be acknowledged and understood. If a state can get away with using these weapons to advance its position, it almost certainly will do so. Large disparities at different levels of nuclear escalation should be avoided if possible, particularly amongst great powers. While developing more destructive and lethal weapons may seem counterproductive to ensuring peace, doing so may not only be in the interest of sustained U.S. hegemony but to prevent the potential use of nuclear weapons and improve international stability.
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