Matthew Kroenig talked about the ethics of nuclear weapons during our annual Christianity and National Security Conference. The following is a transcript of the lecture.

Thank you for that introduction, Mark, and for the invitation to speak today. Thanks to all of you for attending. I look forward to discussing my subject today, ethics and nuclear weapons. I’m a Christian. I was raised Methodist. 

When my wife and I married, we lived in Georgetown, and choosing a church was an important decision. I left it to her—she’s the boss in the family—and she liked Christ Church in Georgetown. We’re members there, both of my children were baptized there, and we enjoy the community. It turns out it’s also a church with many other national security leaders in town, which I didn’t realize. 

This connects to the second part of my life, my work, and my expertise. I’ve focused a lot on nuclear weapons and nuclear strategy over the years. I’ve written seven books, five about nuclear weapons. I’ve worked in the U.S. Department of Defense and the intelligence community in various roles, including on nuclear weapons issues. From 2017 to 2021, I served as a special adviser, special government employee, and senior policy advisor in the Nuclear and Missile Defense Office in the Office of the Secretary of Defense. It was a part-time role—I was teaching at Georgetown, working at the Atlantic Council think tank, and advising in the Department of Defense. I played a major role in drafting the 2018 U.S. Nuclear Posture Review, which remains the United States’ nuclear strategy. The Biden team is currently conducting its own Nuclear Posture Review.

I had these two parts of my life that I hadn’t often put together, but in recent years, partly due to invitations from Mark and Providence, I’ve thought about how these two parts fit together—my Christianity and nuclear weapons and deterrence. I think there is a widespread view that nuclear weapons are immoral and terrible. We saw at Hiroshima and Nagasaki that a single weapon can kill many people. Many Christian churches now seem to adopt the view that the threat of annihilation is immoral, leading to calls for abolishing nuclear weapons. However, I see it differently. I believe U.S. nuclear weapons have been one of the major forces for good in the world over the past 70 years. Specifically, I see U.S. nuclear weapons as special, as opposed to Russian, Chinese, or North Korean nuclear weapons, which I believe don’t play the same role.

You may have heard of the concept of a U.S.-led, rules-based international order established by the United States and its allies after World War II. During the Trump years, one criticism by Biden and others was that Trump was undermining this rules-based order, which has brought about peace, prosperity, and freedom. I do think this U.S.-led rules-based order is special, and I think U.S. nuclear weapons are a central pillar of this order. Without U.S. nuclear weapons, I’m unsure we could have had the peace, prosperity, and freedom we’ve seen over the past 70 years. 

Why do I say that? U.S. nuclear weapons are unique for a couple of reasons. First, U.S. nuclear strategy is different from that of any other country. The United States does not use nuclear weapons solely to defend itself, as Russia, India, and China do. Instead, the United States uses nuclear weapons to defend the entire free world, extending a nuclear umbrella over 30 formal treaty allies—29 other NATO members, South Korea, Australia, and arguably others. We’ve essentially made a deal with these countries, saying, “Don’t build your own nuclear weapons. We think it would be dangerous if all 30 of you had nuclear weapons; instead, rely on U.S. nuclear weapons for your security.” I believe that, through extended deterrence, the United States has played a significant role in preventing the spread of nuclear weapons to other countries. Without this policy, Japan, South Korea, Taiwan, Germany, Poland, and others would likely have nuclear weapons today.

Additionally, U.S. nuclear weapons and extended deterrence have contributed to peace and stability, especially in Europe and Asia, where we have these guarantees. Historically, Europe was the site of major warfare from the beginning of recorded history until 1945. Since 1945, there have been no major power wars in Europe and Asia, and I believe the U.S. nuclear umbrella, or extended deterrence, deterred Russia, China, and North Korea, contributing to this peace. Due to this peace provided by U.S. nuclear weapons, Europe and East Asia have become some of the most prosperous and free parts of the world. Before 1945, only a handful of democracies existed in Europe; today, there are around 30. Before 1945, there were no democracies in Asia, but now Japan, South Korea, Taiwan, and other U.S.-defended countries have developed free institutions. I believe U.S. nuclear weapons served as a protective fence that allowed these gardens of peace, prosperity, and freedom to flourish.

Another unique aspect of U.S. nuclear weapons is counter-force targeting. When people think of nuclear deterrence, they often imagine the U.S. and adversaries threatening to destroy each other’s cities, with everyone deterred by the fear of mass civilian casualties. But this is not how U.S. nuclear strategy has worked for a long time. Instead, the United States practices counter-force targeting, meaning it doesn’t intentionally target innocent civilians. U.S. nuclear targeting aligns with international law and just war theory by focusing on legitimate military targets, such as missile silos, air bases, naval bases, command and control sites, and leadership sites. While some of these targets are located in cities, and nuclear attacks would still result in considerable death and destruction, there is an ethical and practical distinction between intentionally targeting civilians and aiming at legitimate military targets. This principle is foundational to just war theory.

The United States is explicit about this. The 2013 Nuclear Employment Guidance issued by President Obama directed the Department of Defense to practice counter-force targeting partly for ethical and legal reasons. However, counter-force targeting requires a larger nuclear force. If all we wanted was to kill many people in Russia and China, fewer weapons would be needed. But if we’re targeting military sites like air bases and missile silos, that necessitates more warheads. Some ask why the United States needs 1,550 nuclear weapons—the current size of the arsenal—rather than fewer. The main reason is counter-force targeting.

In my 2018 book, I calculated the required number of warheads to cover nuclear and strategic targets in Russia, China, and North Korea. Based on U.S. targeting practices, this came to around 2,000 warheads, which aligns with the current arsenal. Just war theory and international law also emphasize that self-defense is a legitimate reason to use military force. I believe the United States and its allies use nuclear deterrence in self-defense. I mentioned this rules-based system we’ve built over the past 70 years. While not perfect, it’s produced positive outcomes compared to past systems. Since 1945, there have been no great power wars; before then, 1-2% of the world’s population died in conflicts. Today, that figure is a fraction of 1%. The world is more peaceful than before 1945. Prosperity has also increased; poverty has fallen from 66% of the world’s population to around 10%. Standards of living have multiplied since 1945. Freedom has expanded, too; from around 15 democratic countries in 1945, there are now approximately 100.

The world is more peaceful, prosperous, and free than before, and I believe U.S. leadership and nuclear weapons have contributed to this progress. This has been beneficial for the world and for the United States, although our adversaries, particularly Russia and China, dislike it. Russia and China are revisionist powers that aim to dismantle this system. President Putin has explicitly called for “new rules or no rules.” Russia and China are building up their nuclear capabilities to challenge the system. Recent reports indicate China is constructing hundreds of new nuclear silos, testing nuclear-capable hypersonic missiles, and expanding its arsenal, which could quadruple in the next decade. Russia is developing exotic nuclear systems, including nuclear-powered submarines and drones, nuclear-powered cruise missiles, and an array of non-strategic nuclear weapons for various applications. These weapons back Russia’s and China’s revisionist agendas. Both countries have made clear they want the U.S. to disband alliances and allow them to exert influence in Europe and Asia.

In light of this threat, I believe it’s reasonable for the United States and its allies to maintain a strong nuclear deterrent for self-defense, consistent with just war theory. Without a strong deterrent, Russia and China could leverage nuclear weapons to pursue aggressive actions. I believe China’s nuclear buildup partly aims to deter the U.S., giving China more freedom to act against Taiwan and other neighbors.

In short, I view U.S. nuclear weapons as ethical, aligned with just war theory and international law, and as a significant force for good, underpinning this rules-based international system. What does this mean for the future of U.S. nuclear policy? It doesn’t mean the U.S. must always maintain a robust arsenal. The U.S. could reduce its arsenal size or even disarm, but this would come with considerable risks. It would mean abandoning the world order established over the past 70 years, telling allies to develop their nuclear weapons, disregarding international law and just war theory, and relying solely on a limited arsenal for city-targeting. I believe that would be a mistake. However, if the U.S. aims to continue its role in providing global peace and stability, defending allies, and adhering to international law, it will likely need to maintain a robust nuclear arsenal.

I’ll end my talk there and look forward to your questions and comments.

Q&A

Question: Thank you for coming out to talk to us. I’m Rohan from Wheaton College. You talked about how after 1945, when the U.S. launched the nuclear umbrella, it helped reduce poverty. Could you tell us more about how that happened and walk us through the history of how that U.S. action actually helped reduce world poverty?

Answer: The question is how U.S. nuclear weapons relate to world poverty. Good question. I skipped over a lot of history in those 13 minutes. I’m a political scientist, not an economist, but economists have shown that countries in conflict don’t develop as quickly as countries in peace. It makes sense: if you’re fighting wars, you don’t have the peace and stability needed for a stable economic environment that allows for long-term growth. U.S. nuclear weapons have provided that peace, allowing countries to develop. A good example is eastern Europe. After World War II, as they joined this western alliance under the U.S. nuclear umbrella, NATO, and the EU, there was remarkable economic development.

Another piece of this is that U.S. allies don’t have to spend as much of their economy on defense because they rely on U.S. nuclear weapons. This allows them to invest in health care and other areas. This has often been a source of tension in U.S. foreign policy. Trump loudly complained that allies needed to spend more on their defense, but it wasn’t just Trump; going all the way back to Eisenhower, other American presidents asked Europeans to do more for their defense. I think Europeans should do more, and some Asian allies, including Taiwan, should invest more in their defense. But because they haven’t had to invest as much in defense, they’ve been able to invest more in their societies and economic development.

Question: Hi, my name is Natalie. First, thanks for speaking with us. Some argue that increased proliferation could be a positive thing based on mutually assured destruction theories. Where do you think middle powers lie in extended U.S. nuclear deterrence?

Answer: Good question. Some of you may know this proliferation optimism debate. Some scholars, like Kenneth Waltz, argue that nuclear weapon spread is a good thing because nuclear weapons deter war. If every country had nuclear weapons, each would be afraid of every other, and we’d have world peace. One of Waltz’s last articles argued that Iran should get nuclear weapons. Iran would deter us; we’d deter Iran; Iran would deter Israel; Israel would deter Iran, and we’d have peace. 

I think that argument’s mistaken for several reasons. I think it’s not just about technology; it’s about who possesses it and their intentions. The United States has used nuclear weapons to defend the free world and build the world we’ve had for 75 years. I don’t think Iran, Russia, North Korea, and others think about using nuclear weapons the same way. Data shows that North Korea has used nuclear weapons as a backstop for more aggression. Since acquiring nuclear weapons, it has sunk a South Korean warship, shelled a South Korean island, and tried to proliferate nuclear weapons by helping Pakistan and Syria. If every country had nuclear weapons, I don’t think they’d be as responsible as the United States. I think they’d use them as a backstop for aggression and proliferation.

Another problem is a logical contradiction in Waltz’s argument. I do think there are risks with nuclear weapons. As long as they exist, there is a risk they could be used. I don’t think it’s high, but it’s not zero. That risk is why deterrence works. If our adversaries thought there was zero chance the U.S. would use nuclear weapons, deterrence wouldn’t work. But giving every country nuclear weapons increases these risks. I think traditional U.S. nonproliferation policy—maintaining this capability for ourselves but preventing it among both friends and enemies—is the right approach.

Question: Given the buildup of Chinese military and nuclear capabilities, how likely is it that countries like Japan, who rely on the U.S. nuclear umbrella, might feel insecure and proliferate themselves?

Answer: Good question. The U.S. has extended deterrence, trying to convince adversaries not to build nuclear weapons, but we haven’t been completely successful. Britain and France decided during the Cold War that they wanted independent nuclear arsenals. Israel, despite Kennedy Administration persuasion, also built its own. The record has been better in Asia, but there is a possibility that Japan, South Korea, or other countries might decide they need nuclear weapons for their security. South Korea had an illegal nuclear program in the 1970s, and Taiwan had one as well. The U.S. encouraged them to shut down those programs, essentially saying, “Choose between the U.S. security guarantee or nuclear facilities.” They chose the U.S. Japan, South Korea, and Taiwan probably all have the capacity to build nuclear weapons quickly if needed. The question now is demand. 

In Washington, I often discuss this with South Korean and Japanese officials. They say that as long as the U.S. nuclear guarantee is good, they won’t build independent arsenals. But in South Korea, pressure is growing as North Korea builds up its forces. Public opinion polls in South Korea today show that a majority support a nuclear arsenal, although support drops if you ask about doing it even if it upsets China and the U.S. Some prominent South Korean politicians also call for an arsenal. As the U.S. becomes more vulnerable to Chinese nuclear weapons, questions will be raised in Tokyo and Seoul, making reassurance harder. I think we can succeed, but we didn’t always succeed during the Cold War, as Britain, France, and Israel decided to build nuclear weapons. So those countries could go down that path, but for now, it’s in the U.S. interest to extend deterrence and persuade them not to build independent arsenals.

Question: Nate Wate, Liberty University. You talked about counter-force targeting as our strategy instead of mutually assured destruction. But with Hiroshima and Nagasaki, they were also military targets, yet the devastation broke Japan’s will to fight. How does that fit into our strategy compared to breaking the enemy’s will to fight with Russia and China? There would be many civilian casualties.

Answer: Yes, I said the U.S. has never done counter-value targeting, but Hiroshima and Nagasaki are debatable. Jimmy Carter was the first president to be clear on counter-force targeting. His Secretary of Defense, Harold Brown, testified before Congress on its importance, saying, “We’ve always considered it important to target forces that could damage us and our allies.” Every president since has continued this policy. We use counter-force targeting partly for ethical reasons, but there’s a strategic reason as well: the enemy gets a vote. We don’t want nuclear war, but if Russia, China, or North Korea launch a nuclear attack, the U.S. president won’t say, “Okay, we must sit back and accept mutual assured destruction.” We’ll try to defend ourselves and our allies. Every enemy nuclear weapon we destroy on a missile base, air base, or naval base is a weapon not landing on Paris or Washington. That’s the strategic logic behind counter-force targeting.

The essence of deterrence is holding at risk what your adversary values. In the U.S., we value human life and see counter-value targeting as targeting people. For authoritarian rivals, that’s probably not the case. Mao Zedong made blood-curdling statements during the Cold War. In a meeting with Khrushchev, who warned Mao about a possible nuclear conflict with the U.S., Mao replied that even if millions of Chinese were killed, “we’ll just make more Chinese.” For many dictators, what they value more than their people’s lives are their military forces, their lives, and their command and control ability. 

To the point on collateral damage, I agree that in a nuclear exchange, especially a large-scale one, even with counter-force targeting, there would be much death and destruction. But there’s a moral and practical distinction. I’ve done nuclear exchange calculations in my 2018 book, and the differences are substantial, with tens of millions of lives depending on U.S. strategy. I think those lives matter, and the U.S. should try to limit nuclear war damage as part of its strategy. All the way in the back.

Question: Hi, I’m Michael, a graduate student at Harvard studying nuclear policy. It seems as Christians, we have a responsibility to maintain an effective nuclear deterrent, but also to a stable nuclear order with controls on nuclear production internationally. The last few years have seen a breakdown, with the INF Treaty’s end and China’s nuclear buildup. What’s the future of nuclear diplomacy or nuclear reduction? Do we have any hope, or is deterrence our only option?

Answer: Good question. The question is about arms control. There is a bipartisan consensus on nuclear strategy: strong deterrence and strong arms control efforts. Pursuing both makes it easier to get bipartisan and allied consensus. Arms control has been part of U.S. nuclear strategy with Russia since the 1960s-70s and helps limit damage. We do counter-force targeting to limit damage, but arms control also limits damage. One way to get rid of Russian nuclear weapons is to strike them in war; another is to talk and convince them to get rid of them. Arms control can be effective, but it needs an adversary willing to engage and abide by agreements. China has never engaged in arms control. The Obama Administration and the Trump Administration tried to engage China; I suspect the Biden Administration will as well, but under Trump, China was unwilling to even come to the talks, making it difficult.

With Russia, we had arms control in the past, but President Putin in recent years has decided it’s no longer in his interest; he cheated on several arms control agreements. Now, the only remaining agreement is the New START Treaty, which limits both sides to 1,550 nuclear weapons, raising questions about the future of that treaty given the Russian and Chinese buildups.

For background, especially for those not studying nuclear strategy, to get directly to your question: I am worried about the future of arms control. I think it’s a valuable tool, and we should pursue it, but it’s going to be difficult if China won’t even discuss it. There are strategic stability dialogues now between the United States and Russia, but it’s hard to imagine an agreement in the coming years. I think the only solution is an asymmetric agreement. We’re most worried about some of Russia’s non-strategic nuclear weapons that aren’t covered, and they claim to be worried about our missile defenses, so there may be innovative trades where we put limits on missile defenses in exchange for limits on their non-strategic nuclear weapons. An asymmetric deal with China is also possible, but it’s hard to imagine a binding arms control agreement in the next several years. Thank you.

Question: Colleen Quinn from Messiah University. You talked about how American nuclear weapons have led to a rise in democracies globally, yet many younger democracies have fallen into turmoil and unrest. How do you justify more nuclear spending when we could be providing aid to sustain these democracies?

Answer: Good question. The question is about the cost of nuclear weapons. To quote Obama’s Secretary of Defense Ash Carter, nuclear weapons don’t cost that much. The United States spends about five percent of its defense budget on nuclear weapons. Is that too much or too little? Reasonable people can disagree, but every recent Secretary of Defense has said nuclear deterrence is the foremost priority of the U.S. Department of Defense. So, five percent of the defense budget for the top priority seems like a good value.

The question was whether we should provide aid for democracy promotion instead. The United States does have democracy promotion programs—training legislators in the developing world on how the U.S. Congress works to help them develop democratic systems, among other efforts. So, I don’t think it’s either-or; it can be both.