A brief introduction to the just war tradition: Just war and nuclear weapons

September 14, 2017

Note: This is the fifth and final article in a series on the Christian just war tradition.

Imagine North Korean dictator Kim Jong Un announces he will finally implement his family’s long-stated objective of unifying the Korean peninsula. To ensure that no one interferes with his invasion of South Korea, he has hidden his nuclear missiles in the tunnels beneath the DMZ. The dictator threatens that these weapons, which can quickly be moved out of the tunnels, will be launched against Seoul, Guam, and Japan if South Korea, the U.S., or any other nation interferes with his plan.

The Western democracies are left with only two options: They can concede to North Korea’s demands and allow the enslavement of millions of people, or they can launch a preemptive nuclear strike using bunker-buster tactical nukes.

What should a Christian leader do? Would it be possible to use nuclear weapons in this situation in a way that aligns with the just war tradition?

It's never moral to use nuclear weapons on civilian targets, such as enemy cities.

Unfortunately, many of us don’t know how to provide a moral answer to these questions. Theological reflection on the use of nuclear weapons has always been lacking within American churches, and such thought tends to focus on apologies for the use of the atomic bombs on Nagasaki and Hiroshima.* Since the end of the Cold War, almost no fresh thinking has been given to the subject at all by the broader evangelical community.

The most thoughtful consideration of nuclear weapons has tended to come from pacifist groups, such as Anabaptists, and others who support complete nuclear abolitionism. They tend to start with the view that nuclear weapons are intrinsically evil and their use objectively immoral, thus making them illegitimate for any use in just warfare.

Less consideration has been given by those of us who begin with the just war tradition and then attempt to explain how (or even if) nuclear arms can fit within a just war framework. In this article, I want to attempt to provide a model for such reflection by applying what we’ve learned in earlier articles in this series to consider under what conditions nuclear weapons might be acceptable.

When would it be morally legitimate to use nukes?

Let’s begin by assuming that the use of nuclear weapons is being considered in a conflict that meets all of the jus ad bellum criteria. That means the weapons would be considered primarily from a jus in bello perspective (the criteria for justly engaging in warfare), and to a lesser extent, from the jus post bellum perspective, (justice after war).

Nuclear weapons can be either tactical or strategic. A tactical nuclear weapon is a nuclear weapon designed for use on a battlefield in military situations, where friendly forces may be in relatively close proximity. A strategic nuclear weapon refers to a nuclear weapon designed to be used on targets in territory far from the battlefield as part of a strategic plan, such as on military bases, weapons factories, or military command centers.

Whether the weapons are tactical or strategic, their use should align with the two primary criteria for just execution of war, discrimination and proportionality.

As we discussed in a previous article in this series, the criterion of discrimination includes two key components, “innocence” and “deliberate attack.” The first rule of just warfare is that we do not target or kill the innocent. Nuclear weapons must therefore never be used to target noncombatants (i.e., women, children, the aged and infirm, etc.).

This is related to the second component of discrimination—“deliberate attack.” While the innocent may be harmed because of our engaging in warfare—such as when civilians are used as “human shields”—it must not be our intention to deliberately attack them. For this reason, nuclear weapons must not be used on civilian targets; enemy cities cannot be targeted for deliberate attack, even in retaliation. As Rebeccah Heinrichs says,

[U]nder no circumstances should the United States target civilian populations. Targeting civilians violates the fundamental principles that define the character of the United States of America and fails to meet the just war criteria jus in bello. Moreover, even from the perspective of cold realism, claiming to target civilian populations and maintaining a force structure designed to do this would likely not serve American interests, for some enemy leaders do not value the lives of their civilian populations the way that the United States does. In fact, it is reasonable to assert that American policymakers value the lives of enemy countries’ civilians more than their dictators do.

This is why Christians who accept both nuclear weapons and the just war tradition should support a nuclear strategy of counterforce targeting (using nuclear weapons only for military targets) rather than countervalue targeting (targeting of an opponent's assets which are of value but not actually a military threat, such as cities and civilian populations). See Heinrich’s article for more on how a counterforce strategy of deterrence is compatible with the just war tradition.

The second major jus in bello criterion is proportionality. As Jean Bethke Elshtain explains, proportionality “requires that the nature of one’s coercive force should be proportional to any injury sustained or planned, and that at whatever minimal force can be used to do the job should be deployed.” In the context of nuclear weapons, this would require that we should not use a high-yield weapon that has significant long-term effects (such as nuclear fallout) if it is possible to achieve the same military objective with conventional weapons.

In addition to these jus in bello criteria, there is a jus post bellum principle we must consider: the effect on the subsequent maintenance of reasonable living conditions and order for the people of the country where the nuclear weapons are used.

Now let’s apply these principles to our original North Korean scenario. Because the nuclear weapons would be used on a military target with few or no civilians in the area, it would likely pass the test of discrimination. Similarly, the criterion of proportionality may be met if the military commanders determine that non-nuclear bombs are unable to destroy the North Korean nuclear missiles.

Likewise, the area around the bombing may be subjected to nuclear fallout, but that would likely be a lesser harm than allowing the North Koreans to launch a nuclear attack.


While the North Korea scenario is a limited and narrow example, it provides an illustration of how Christians can and should apply just war principles to thinking about when the use of nuclear weapons might be appropriate. Nuclear weapons have neither made the just war tradition obsolete, nor added a significant layer of complexity. “Nuclear weapons do represent a novel and terrifying development in the history of international violence,” says just war theorist Robert L. Phillips, “ but as a form of state initiated force they demand the same kind of scrutiny and moral appraisal as any other kind of weapons system.”

Whether the weapons are slingshots or intercontinental ballistic missiles, Christians have inherited a robust tradition and framework to think morally about how warfare should be conducted.

*Because the debate about the use of nuclear weapons involves a significant degree of complexity, I’ve chosen to avoid discussing it in this article. For now I want to focus on future-oriented consideration of nuclear weapons.

Joe Carter

Joe Carter is the author of The Life and Faith Field Guide for Parents, the editor of the NIV Lifehacks Bible, and the co-author of How to Argue Like Jesus: Learning Persuasion from History’s Greatest Communicator. He also serves as an executive pastor at the McLean Bible Church Arlington location in Arlington, Virginia. Read More

Article 12: The Future of AI

We affirm that AI will continue to be developed in ways that we cannot currently imagine or understand, including AI that will far surpass many human abilities. God alone has the power to create life, and no future advancements in AI will usurp Him as the Creator of life. The church has a unique role in proclaiming human dignity for all and calling for the humane use of AI in all aspects of society.

We deny that AI will make us more or less human, or that AI will ever obtain a coequal level of worth, dignity, or value to image-bearers. Future advancements in AI will not ultimately fulfill our longings for a perfect world. While we are not able to comprehend or know the future, we do not fear what is to come because we know that God is omniscient and that nothing we create will be able to thwart His redemptive plan for creation or to supplant humanity as His image-bearers.

Genesis 1; Isaiah 42:8; Romans 1:20-21; 5:2; Ephesians 1:4-6; 2 Timothy 1:7-9; Revelation 5:9-10

Article 11: Public Policy

We affirm that the fundamental purposes of government are to protect human beings from harm, punish those who do evil, uphold civil liberties, and to commend those who do good. The public has a role in shaping and crafting policies concerning the use of AI in society, and these decisions should not be left to those who develop these technologies or to governments to set norms.

We deny that AI should be used by governments, corporations, or any entity to infringe upon God-given human rights. AI, even in a highly advanced state, should never be delegated the governing authority that has been granted by an all-sovereign God to human beings alone. 

Romans 13:1-7; Acts 10:35; 1 Peter 2:13-14

Article 10: War

We affirm that the use of AI in warfare should be governed by love of neighbor and the principles of just war. The use of AI may mitigate the loss of human life, provide greater protection of non-combatants, and inform better policymaking. Any lethal action conducted or substantially enabled by AI must employ 5 human oversight or review. All defense-related AI applications, such as underlying data and decision-making processes, must be subject to continual review by legitimate authorities. When these systems are deployed, human agents bear full moral responsibility for any actions taken by the system.

We deny that human agency or moral culpability in war can be delegated to AI. No nation or group has the right to use AI to carry out genocide, terrorism, torture, or other war crimes.

Genesis 4:10; Isaiah 1:16-17; Psalm 37:28; Matthew 5:44; 22:37-39; Romans 13:4

Article 9: Security

We affirm that AI has legitimate applications in policing, intelligence, surveillance, investigation, and other uses supporting the government’s responsibility to respect human rights, to protect and preserve human life, and to pursue justice in a flourishing society.

We deny that AI should be employed for safety and security applications in ways that seek to dehumanize, depersonalize, or harm our fellow human beings. We condemn the use of AI to suppress free expression or other basic human rights granted by God to all human beings.

Romans 13:1-7; 1 Peter 2:13-14

Article 8: Data & Privacy

We affirm that privacy and personal property are intertwined individual rights and choices that should not be violated by governments, corporations, nation-states, and other groups, even in the pursuit of the common good. While God knows all things, it is neither wise nor obligatory to have every detail of one’s life open to society.

We deny the manipulative and coercive uses of data and AI in ways that are inconsistent with the love of God and love of neighbor. Data collection practices should conform to ethical guidelines that uphold the dignity of all people. We further deny that consent, even informed consent, although requisite, is the only necessary ethical standard for the collection, manipulation, or exploitation of personal data—individually or in the aggregate. AI should not be employed in ways that distort truth through the use of generative applications. Data should not be mishandled, misused, or abused for sinful purposes to reinforce bias, strengthen the powerful, or demean the weak.

Exodus 20:15, Psalm 147:5; Isaiah 40:13-14; Matthew 10:16 Galatians 6:2; Hebrews 4:12-13; 1 John 1:7 

Article 7: Work

We affirm that work is part of God’s plan for human beings participating in the cultivation and stewardship of creation. The divine pattern is one of labor and rest in healthy proportion to each other. Our view of work should not be confined to commercial activity; it must also include the many ways that human beings serve each other through their efforts. AI can be used in ways that aid our work or allow us to make fuller use of our gifts. The church has a Spirit-empowered responsibility to help care for those who lose jobs and to encourage individuals, communities, employers, and governments to find ways to invest in the development of human beings and continue making vocational contributions to our lives together.

We deny that human worth and dignity is reducible to an individual’s economic contributions to society alone. Humanity should not use AI and other technological innovations as a reason to move toward lives of pure leisure even if greater social wealth creates such possibilities.

Genesis 1:27; 2:5; 2:15; Isaiah 65:21-24; Romans 12:6-8; Ephesians 4:11-16

Article 6: Sexuality

We affirm the goodness of God’s design for human sexuality which prescribes the sexual union to be an exclusive relationship between a man and a woman in the lifelong covenant of marriage.

We deny that the pursuit of sexual pleasure is a justification for the development or use of AI, and we condemn the objectification of humans that results from employing AI for sexual purposes. AI should not intrude upon or substitute for the biblical expression of sexuality between a husband and wife according to God’s design for human marriage.

Genesis 1:26-29; 2:18-25; Matthew 5:27-30; 1 Thess 4:3-4

Article 5: Bias

We affirm that, as a tool created by humans, AI will be inherently subject to bias and that these biases must be accounted for, minimized, or removed through continual human oversight and discretion. AI should be designed and used in such ways that treat all human beings as having equal worth and dignity. AI should be utilized as a tool to identify and eliminate bias inherent in human decision-making.

We deny that AI should be designed or used in ways that violate the fundamental principle of human dignity for all people. Neither should AI be used in ways that reinforce or further any ideology or agenda, seeking to subjugate human autonomy under the power of the state.

Micah 6:8; John 13:34; Galatians 3:28-29; 5:13-14; Philippians 2:3-4; Romans 12:10

Article 4: Medicine

We affirm that AI-related advances in medical technologies are expressions of God’s common grace through and for people created in His image and that these advances will increase our capacity to provide enhanced medical diagnostics and therapeutic interventions as we seek to care for all people. These advances should be guided by basic principles of medical ethics, including beneficence, non-maleficence, autonomy, and justice, which are all consistent with the biblical principle of loving our neighbor.

We deny that death and disease—effects of the Fall—can ultimately be eradicated apart from Jesus Christ. Utilitarian applications regarding healthcare distribution should not override the dignity of human life. Fur- 3 thermore, we reject the materialist and consequentialist worldview that understands medical applications of AI as a means of improving, changing, or completing human beings.

Matthew 5:45; John 11:25-26; 1 Corinthians 15:55-57; Galatians 6:2; Philippians 2:4

Article 3: Relationship of AI & Humanity

We affirm the use of AI to inform and aid human reasoning and moral decision-making because it is a tool that excels at processing data and making determinations, which often mimics or exceeds human ability. While AI excels in data-based computation, technology is incapable of possessing the capacity for moral agency or responsibility.

We deny that humans can or should cede our moral accountability or responsibilities to any form of AI that will ever be created. Only humanity will be judged by God on the basis of our actions and that of the tools we create. While technology can be created with a moral use in view, it is not a moral agent. Humans alone bear the responsibility for moral decision making.

Romans 2:6-8; Galatians 5:19-21; 2 Peter 1:5-8; 1 John 2:1

Article 2: AI as Technology

We affirm that the development of AI is a demonstration of the unique creative abilities of human beings. When AI is employed in accordance with God’s moral will, it is an example of man’s obedience to the divine command to steward creation and to honor Him. We believe in innovation for the glory of God, the sake of human flourishing, and the love of neighbor. While we acknowledge the reality of the Fall and its consequences on human nature and human innovation, technology can be used in society to uphold human dignity. As a part of our God-given creative nature, human beings should develop and harness technology in ways that lead to greater flourishing and the alleviation of human suffering.

We deny that the use of AI is morally neutral. It is not worthy of man’s hope, worship, or love. Since the Lord Jesus alone can atone for sin and reconcile humanity to its Creator, technology such as AI cannot fulfill humanity’s ultimate needs. We further deny the goodness and benefit of any application of AI that devalues or degrades the dignity and worth of another human being. 

Genesis 2:25; Exodus 20:3; 31:1-11; Proverbs 16:4; Matthew 22:37-40; Romans 3:23

Article 1: Image of God

We affirm that God created each human being in His image with intrinsic and equal worth, dignity, and moral agency, distinct from all creation, and that humanity’s creativity is intended to reflect God’s creative pattern.

We deny that any part of creation, including any form of technology, should ever be used to usurp or subvert the dominion and stewardship which has been entrusted solely to humanity by God; nor should technology be assigned a level of human identity, worth, dignity, or moral agency.

Genesis 1:26-28; 5:1-2; Isaiah 43:6-7; Jeremiah 1:5; John 13:34; Colossians 1:16; 3:10; Ephesians 4:24