Since the atomic bombings of Hiroshima and Nagasaki, there’s been a nearly universal appreciation for the terrible destructiveness of nuclear weapons—their capacity to extinguish human civilization itself. Although chemical and biological weapons are also regarded as weapons of mass destruction (WMDs), nuclear weapons stand apart due to the scale of devastation and the very short time needed to wreak it. Catholic teaching to date has singled out such weapons for special consideration regarding the morality of their use in war. Historically, such consideration has taken a highly nuanced approach to the question of nuclear deterrence, specifically whether using the threat of nuclear retaliation to discourage adversaries from attacking is as morally repugnant as actually using nuclear weapons in war-fighting.
In the documents of Vatican II (Gaudium et spes), we read that the use of “scientific weapons” to inflict massive and indiscriminate destruction on entire cities constitutes a “crime against God.” Deterrence, the document argues, “is not a safe way to preserve a steady peace, nor is the so-called balance resulting from this [arms] race a sure and authentic peace.” Yet the Council didn’t call for the immediate abandonment of deterrence, and it acknowledged the profound challenge that governments face as they claw out of the predicament of modern war:
Since peace must be born of mutual trust between nations and not be imposed on them through fear of the available weapons, everyone must labor to put an end at last to the arms race, and to make a true beginning of disarmament, not unilaterally indeed, but proceeding at an equal pace according to agreement, and backed up by true and workable safeguards.
Pope St. John Paul II—who uniquely understood the dangers of totalitarian ideologies to the safety and security of the world—proclaimed a definitive conditioned moral acceptance of nuclear deterrence. In a speech to the UN General Assembly in 1982, he stated:
In current conditions “deterrence” based on balance, certainly not as an end, but as a step on the way toward a progressive disarmament, may still be judged morally acceptable. Nonetheless in order to ensure peace, it is indispensable not to be satisfied with this minimum which is always susceptible to the real danger of explosion.
In 2017, Pope Francis signaled a fundamental shift in the Church’s traditional views on nuclear weapons in conjunction with the Vatican’s accession to the Treaty on the Prohibition of Nuclear Weapons (TPNW). (Note this so-called “treaty” is aspirational only, containing no verification or enforcement provisions.) At an international symposium in November of that year, the pope publicly condemned nuclear weapons, stating: “If we also take into account the risk of accidental detonation as a result of error of any kind, the threat of their use, as well as their very possession, is to be firmly condemned.” By implication he was damning nuclear deterrence, and other Church leaders have followed suit in the ensuing years.
Until now, the Church has relied on a collected set of fundamental moral principles to balance its prohibition against taking innocent life with recognition of governments’ duty to defend their civil societies against aggressors employing armed force. These principles are codified in just-war doctrine, which goes back centuries, to the deliberations and writings of Saints Augustine and Thomas Aquinas. The doctrine recognizes the inherent challenges faced by the “Church Militant” on Earth, as opposed to presupposing the conditions of the “Church Triumphant” in heaven. It reflects the reality of the universal struggle between good and evil that inevitably stems from the stain of sin on the collective soul of humanity. In fact, just-war doctrine has had a significant influence on the formulation of the U.S. law of armed conflict, which establishes ethical standards for the Department of Defense’s Law of War Manual.
The advent of modern weapons technology, particularly WMDs but conventional arms as well, presents challenges for just-war doctrine, especially its jus in bello principles governing conduct in war, as opposed to the jus ad bellum principles for determining whether to go to war. The former include a duty to discriminate between combatants and innocents and to maintain proportionality between the costs of given military actions and their societal benefits. The horrific weapons of modern warfare make it more difficult to focus death and destruction on military targets alone while sparing innocent civilians. To take one example, the strategic incendiary bombing of sixty-six major industrial Japanese cities created fire storms that decimated 178 square miles. The geopolitical context of modern warfare has also changed significantly with the formation of multinational alliances, which can quickly escalate conflicts to a global scale.
The principles of just-war doctrine must be continually reexamined in the face of these historic changes. But they need not and should not be abandoned. Just-war doctrine should remain relevant to the design and implementation of military technologies, including the evolution and development of nuclear weapons.
The Church’s recent shift away from just-war doctrine and its emphasis on nuclear disarmament represent, in the terms of international relations, a preference for idealism over realism. Idealists put their faith in multinational institutions and unified global governance that will solve all problems between states, making war and nuclear weapons obsolete. This global authority (as vested in the United Nations, for example) is also to be called upon to enforce international rules. On this model, national leaders would place the good of humanity ahead of national power or sovereignty. Nuclear disarmament would be achieved as separate nations together surrender all their nuclear weapons to the global authority and rely on that authority for security.
Unfortunately, humanity’s collective consciousness has simply not yet reached the level required to sustain such an order. Realists have a more tragic outlook; they see history, as Rebeccah Heinrichs writes, “as moving down a timeline wherein peace, conflict, and war come and go.” Unable to trust each other, nations seek power in line with their own security interests in a chaotic world. These interests drive countries to pursue and acquire nuclear weapons. Just-war doctrine is clearly more aligned with the realist school, explicitly acknowledging the fallen, sinful nature of humanity. By its lights, the consciousness needed for idealist policy to be effective may only come in the bliss of beatific life realized in the eschaton. Just-war doctrine addresses the world as it is, with recurring wars and persistent dangers, and seeks to minimize war and its costs and protect the innocent. It also seeks to inform difficult decisions about military doctrine and technology with justifiable moral norms.
In our fallen world and rapidly evolving global security environment, nuclear deterrence remains the foundation of U.S. national security. The threat of nuclear retaliation is the basis of a U.S. nuclear strategy focused on deterring adversaries from launching any initial nuclear attack against our nation or against allies and partners covered by the U.S. nuclear umbrella. This “extended deterrence” strategy supports today’s global nonproliferation norms by obviating the need for allies to develop their own nuclear arsenals.
The cornerstone for the ethical possession of nuclear weapons for the purpose of deterrence was pronounced by President Ronald Reagan in his 1984 State of the Union address (later echoed by Soviet leader Mikhail Gorbachev in 1986): “A nuclear war cannot be won and must never be fought.” Of course, to never be fought, a nuclear war must also never be initiated. Morality is ultimately not determined by the presence or nature of weapons alone, but by the intentions behind their use. As Reagan states, the fundamental intention of a nuclear deterrent is, first and foremost, to prevent any initiation of hostile nuclear attack in the first place.
The full moral significance of this intention can perhaps be better understood by recognizing it as two subsistent intentions acting together. Whereas the fundamental, declared moral intention is to avoid having to order a retaliatory nuclear strike by dissuading any initial nuclear strike, there is a secondary supporting intention on which the credibility and effectiveness of deterrence rests. This secondary intention involves the expressed political and public will to employ the deterrent nuclear force in the first place. This must be backed up by an entire infrastructure, including an open process of government policymaking and budgeting, weapons research and development, deployment, maintenance, and command-and-control systems.
This secondary intention must be clearly perceived by potential aggressors, lest they interpret the declared deterrence policy as a bluff, perhaps even precipitating the very nightmare it seeks to avoid. Once a strategic or battlefield nuclear attack does occur, deterrence has failed. Just-war doctrine would then consider the primary moral imperative to be the earliest termination of hostilities. That would entail a response at the lowest possible rung of the escalation ladder, with either conventional or nuclear arms, and a negotiation process to end the conflict and restore justice. This is clearly not the fatalistic policy of mutually assured destruction—the immoral, Cold War–era policy that critics often cite as a general characteristic of every kind of deterrence.
Deterrence is a dynamic rather than a static strategic posture. The U.S. nuclear arsenal must adapt to evolving global geopolitical realities, change its delivery systems, and force its configurations to align with shifts in strategic policy. Since the Comprehensive Nuclear-Test-Ban Treaty of 1996, these changes must be accommodated without explosive testing. But technological improvements through the years have enabled nuclear weapons to be more closely aligned with just-war principles.
For example, lower-yield nuclear weapons (possibly with greater accuracy) can be deployed to allow more flexible response options intended to deter lower-scale battlefield and regional nuclear attacks. They also enable strategic targeting away from civilian population centers toward military or leadership targets that hold the most value to the adversary. Finally, anti-ballistic-missile defensive technology has come a long way since the days of “Star Wars.” Active and passive defensive measures, in addition to credible deterrence, have enabled the United States to move steadily toward a more moral strategic policy.
The First Nuclear Age was characterized by the bilateral Cold War standoff between two nuclear superpowers. The Second, precipitated by the collapse of the Soviet Union, was primarily a denuclearization paradigm focused on nonproliferation and, following 9/11, preventing terrorists from acquiring nuclear weapons and securing nuclear materials more broadly.
However, two events signal the reemergence of strategic superpower competition and the birth of a Third Nuclear Age. One was the Russian invasion of Ukraine in February 2022—a clear violation of just-war thinking as well as a direct contravention of the postwar liberal international order (and the Budapest Memorandum of 1994). The second involved the discovery in 2021 of 120 Chinese intercontinental-ballistic-missile silos under construction at the edge of the Gobi Desert, as well as an additional 110 silos underway in Xinjiang province. Given its parallel development of multiple independently targetable reentry vehicles to be deployed on new Chinese missiles, it was easy to see that China was breaking out of the class of “minor” nuclear powers. It will likely soon join the United States and the Russian Federation as a third nuclear superpower.
A new world order involving hostile relationships among three nuclear-armed superpowers demands a multipolar nuclear-deterrence paradigm. The challenges of creating one are unprecedented and perhaps insurmountable. Game theory, frequently used in the First Nuclear Age as an analytical tool to quantify the relationship between the USSR and the United States (a “two-body” problem), will not suffice in the Third Nuclear Age. The analytical challenges make opportunities for negotiated and verifiable nuclear-arms control all the more precious.
But in too many Church deliberations and pronouncements, the importance of mutual and verifiable arms reductions is presented only as an afterthought. The Church vastly underemphasizes the intrinsic difficulties involved in negotiation, planning, and execution. If strategic arms control is to develop beyond New START, monitoring and verification procedures would need to be enhanced and extended. They would require an on-site presence capable of direct accounting for warheads, their components and subsystems, and eventually even quantities of nuclear materials. The level of mutual trust necessary among the global superpowers would be unparalleled in world history.
Moving from this stage to a “world without nuclear weapons” would require a monitoring and verification effort more challenging, comprehensive, and systematic. Bilateral negotiations would have to become multilateral negotiations, involving a global set of participants, all aspects of nuclear-weapon life cycles, and even civilian nuclear-energy fuel cycles. Nothing short of unprecedented trust and unending verification efforts would be needed. Given the chaotic state of international relations today, we are still a far cry from these goals.
Unfortunately, in the world as it exists, fear tends to have a stronger influence than inspiration derived from fraternal love. Deterrence, rooted in fear, has proven effective in preventing major power conflict throughout the Cold War and for thirty-five years after the Soviet Union’s collapse. Nuclear peace conditioned totally on deterrence is certainly fragile, as the challenges of the Third Nuclear Age show. But unilateral nuclear disarmament would expose the disarming nation to needless and grave risks; it would be an ineffective, as well as morally repugnant, means for attaining peace. Hasty measures at reforming or abandoning the deterrence paradigm would be similarly dangerous. We must believe that deterrence complemented by continuing efforts at genuine negotiated arms control can be more successful at preventing nuclear annihilation into the future.
War will persist as long as there is sin, and fear can easily engender social fragmentation, hatred, and war. True peace is found not merely in the absence of conflict (e.g., Pax Romana) or eliminating any particular type of weapon, but in the formation of an abiding relationship with Christ that transforms the human heart fundamentally and engenders universal respect for the dignity of all humans. This is arguably the challenge for our Church today. It must orient itself toward providing the spiritual guidance needed by the Church Militant, rather than seeking to directly enter the fray of international politics. Transforming and healing the “heart of humanity” must also extend to all humankind, including the people of Russia, China, Iran, and North Korea.
By allowing human beings to understand and then control the physical forces of the atomic nucleus, God has, at the same time, challenged us to rise above our fallen nature and work with him in preventing the annihilation we all abhor. But we must proceed prudently, not losing sight of the fact that such a transformation will not be accomplished overnight.
This article was published as part of a symposium titled “The Path Toward Disarmament.” The other contributions to the symposium can be found here:
Archbishop John Wester, “A First Step”
Maryann Cusimano Love, “The Promise of Peacebuilding”
J. Bryan Hehir, “A Pluralistic Ethic”
