Strengthening the Nuclear Taboo in the Midst of Russia’s War on Ukraine

One year ago, Russian President Vladimir Putin unleashed a massive invasion on independent, democratic, non-nuclear Ukraine that has killed thousands, displaced millions, and created economic, social, and political disruption on a global scale.

Putin’s war, along with his implied threats of nuclear weapons use against any who would interfere, has also raised the specter of a nuclear conflict in ways not seen in the post-Cold War era. It has also derailed bilateral U.S.-Russian talks on implementation of existing and new arms control measures.

If nuclear weapons are used in this conflict or any between nuclear-armed adversaries, we are in uncharted territory. Theories that a nuclear war can be “limited” are just theories. Once and if nuclear weapons are used in a conflict involving the United States and Russia, there is no guarantee it would not quickly become an all-out nuclear conflagration.

As U.S. President Joe Biden warned Oct. 6, 2022, “I don’t think there’s any such thing as an ability to easily use a tactical nuclear weapon and not end up with Armageddon.”

A recent Princeton Program on Science and Global Security simulation estimates the use of nuclear weapons in war between NATO and Russian forces that begins with a small number of nuclear detonations from short-range systems in a regional war could quickly escalate and lead to the death and injury of nearly 100 million people in just the first few hours.

So far, the 78-year-old taboo against the use of nuclear weapons has held, but we cannot take for granted. Tragically, the end of the war is nowhere in sight, and the danger of nuclear escalation still looms.

To preserve and strengthen the consensus against nuclear weapons use and threats of use, civil society and the international community must sustain pressure against those who might try to break the nuclear taboo.

The Nuclear Dimensions of the War

In FebruaryApril, and September 2022, Putin made veiled threats of nuclear weapons use in the event that any state attempts to interfere in Russia’s massive military assault on Ukraine.

“No matter who tries to stand in our way … they must know that Russia will respond immediately, and the consequences will be such as you have never seen in your entire history,” Putin said Feb. 24.

During a televised meeting Feb. 27, Putin ordered the Russian defense minister, Sergey Shoygu, and the chief of the military’s general staff, Valery Gerasimov, to put Russia’s long-range nuclear forces on a “special regime of combat duty.” Putin described the move as a response to NATO powers’ making what he called “aggressive statements.”

Putin’s order most likely served as a preliminary command designed to bring Russia’s strategic nuclear systems into a working condition, not necessarily to prepare those forces to carry out a first strike. Nevertheless, the command was a provocative nuclear signal designed to intimidate.

Two months later, Putin reiterated his warning against outside interference in Ukraine that “creates an unacceptable threat of a strategic nature for Russia,” saying that the Russian response “lightning-fast [as] decisions on this matter have been made.”

Both the United States and the Soviet Union issued various kinds of nuclear threats and alerts during the Cold War, before the 1962 Cuban missile crisis and after. However, Russia’s current implied nuclear threats to shield an attack by a nuclear-armed state against a non-nuclear-weapon state are unprecedented—and unacceptable—in the post-Cold War era. Plus, since the Soviet Union’s dissolution in 1991, no U.S. or Russian leader has raised the alert level of nuclear forces to try to coerce a potential nuclear adversary’s behavior.

To his credit, Biden has not responded by issuing reciprocal threats against Russia or by raising the alert levels of U.S. nuclear forces. Instead, Biden has reaffirmed that U.S. and NATO forces would not become engaged directly in the war, while still providing the necessary assistance to help Ukrainians defend their country.

“We won’t be intimidated by Putin’s rhetoric,” the White House emphasized in October. This stance took the punch out of Putin’s threats and has, so far, helped ensure that the Russian nuclear bully does not get his way.

But in the early weeks of the all-out Russian invasion, Biden simply referred to Russia’s “occasional nuclear rhetoric” as “dangerous and extremely irresponsible,” implying that some types of nuclear threats are “responsible.” The United States and NATO, of course, exercise similar deterrence strategies that rely on the credible threat of nuclear weapons use.

France, the United Kingdom, and the United States expanded on this theme in a July joint working paper, in which they asserted that their nuclear weapons only “serve defensive purposes, deter aggression and prevent war.”

Not surprisingly, Russian officials claimed Putin’s nuclear warnings also serve “defensive” purposes, and are simply designed intended to deter Western interference.

However, from a legal perspective, the International Court of Justice unanimously determined in its 1996 advisory opinion that a threat to engage in nuclear weapons use, particularly under the circumstances suggested by Putin, stands contrary to international humanitarian law, and that the threat to use nuclear weapons violates the UN Charter.

Putin’s threats also clearly violate the 1973 bilateral Agreement on the Prevention of Nuclear War, which pledged the United States and the Soviet Union to “refrain from the threat or use of force against the other Party, against the allies of the other Party and against other countries, in circumstances which may endanger international peace and security.”

Importantly, the 2017 Treaty on the Prohibition of Nuclear Weapons (TPNW), which entered into force in 2021 and has the support of some 130 states, prohibits not only the possession, development, testing, transfer, and use of nuclear weapons, but also threats of use.

Efforts to Reinforce the Nuclear Taboo in 2022

In contrast to the caveated criticism from Washington, London, and Paris in the first half of 2022, many leaders from non-nuclear-weapon states recognized that Putin’s brazen nuclear threats made in the context of a war against a non-nuclear weapon state required them to speak with greater clarity to avert a nuclear catastrophe. And they did.

In June 2022, the then 65 TPNW states-parties issued a political statement noting that “any use or threat of use of nuclear weapons is a violation of international law, including the Charter of the United Nations,” and condemning “unequivocally any and all nuclear threats, whether they be explicit or implicit and irrespective of the circumstances.”

At the nuclear Nonproliferation Treaty (NPT) review conference in August, a group of 147 non-nuclear-weapon states declared the use of nuclear weapons unacceptable “under any circumstances.”

Nevertheless, on Sept. 21, as Russian forces were in retreat in eastern Ukraine, Putin suggested he might order the use of shorter-range nuclear weapons “if the territorial integrity of our country is threatened,” including the territory in Ukraine that Russia had illegally seized. “This is not a bluff,” he added.

In this context, Putin’s threats implied that, if he believes there is an attack on Russian territory or on Ukrainian territory illegally claimed by Russia, he might order the use of tactical nuclear weapons to decimate Ukraine’s defense forces or its cities, demonstrate Russian resolve, and attempt to force Ukraine and its allies to surrender.

Subsequently, press reports revealed that, according to U.S. intelligence agencies, senior Russian military officials discussed when and how Moscow might use a tactical nuclear weapon in Ukraine.

Putin’s September threat clearly veered away from Russia’s official nuclear doctrine, which reserves the option to use nuclear weapons in response to an attack with weapons of mass destruction or if a conventional war threatens the “very existence of the state.”

In response to Putin’s stronger nuclear threat rhetoric, key leaders and nuclear experts began to speak out in starker and more direct terms. And for good reason.

In an interview with CBS News’s “60 Minutes” that aired Sept. 16, Biden was asked what he would tell Putin if the Russian leader is considering using nuclear weapons in the conflict against Ukraine. “Don’t. Don’t. Don’t,” Biden said. “You will change the face of war unlike anything since World War II.” He wisely declined to detail how the United States would respond to Russian nuclear weapon use in Ukraine, saying only that the reaction would be “consequential” and would depend “on the extent of what they do.”

As I said in a report by The Washington Post on Sept. 22: “What everyone needs to recognize is that this is one of, if not the most, severe episodes in which nuclear weapons might be used in decades. The consequences of even a so-called ‘limited nuclear war’ would be absolutely catastrophic.”

A few days later, White House National Security Advisor Jake Sullivan disclosed that the United States has warned Russia of “catastrophic consequences” if Russia uses nuclear weapons.

NATO Secretary-General Jens Stoltenberg also weighed in. Borrowing from the terminology used by the non-nuclear-weapon states in their June and August statements. “Any use of nuclear weapons is absolutely unacceptable,” he said on Sept. 27.

President Joe Biden said Oct. 6 that the “prospect of Armageddon” the highest since the 1962 Cuban Missile Crisis.

German Chancellor Olaf Scholz declared Oct. 8, “We need to give a clear answer to nuclear threats. They’re dangerous for the world, and the use of nuclear weapons is unacceptable.” Perhaps more importantly, leaders who previously remained silent about Putin’s nuclear threats finally spoke up. Chinese President Xi Jinping said Nov. 4 that the international community should “jointly oppose the use of, or threats to use, nuclear weapons.”

Then, the powerful Group of 20 (G-20) nations issued Nov. 16 a statement at their summit declaring that the use of nuclear weapons and threats of use are “inadmissible.” The strong G-20 language – endorsed by its members, including Brazil, India, Indonesia, Japan, Mexico, Saudi Arabia, South Africa, South Korea, and Turkey – was due in large part to the efforts of the host nation, Indonesia, a TPNW supporter.

By the end of 2022, Putin appeared to back off his threats of nuclear weapon use. “We see no need” to use nuclear weapons in Ukraine, he said in October. “There is no point in that, neither political nor military.”

This rhetorical retreat was no accident. Undoubtedly, Putin’s advisers – as well as U.S. and NATO leaders – reminded the Russian president that there is no military value in using nuclear weapons against Ukrainian targets. Instead of ending the war, such an atrocity would almost certainly draw NATO into the conflict, bringing about Russia’s defeat and Putin’s own downfall.

German Foreign Minister Annalena Baerbock said in a Feb. 11, 2023 interview with Tagasspiegelthat she saw a link between G-20 statement on about on nuclear threats being “inadmissible” and reduced Russian nuclear rhetoric since November 2022. Global norms do have an impact on the nuclear policies of autocratic states after all.

Reinforcing the Nuclear Taboo in 2023

On the one-year anniversary of the start of the Russian invasion, the UN the European Union will advance a resolution at a high-level emergency session of the UN General Assembly calling for a cessation of hostilities and a peace that ensures Ukraine’s “sovereignty, independence, unity and territorial integrity.”

Such efforts are crucial even if they do not yield immediate results. The UN charter calls for peaceful settlement of disputes and declares that all countries shall refrain “from the threat or use of force against the territorial integrity or political independence of any state.”

But as Russia continues to try to find a way to “win” its war on Ukraine and as the Ukrainian people continue to valiantly resist, the fighting and bloodshed and the danger of escalation will continue. Although the threat of nuclear weapons use by Russia may have receded since the fall of 2022, it has not gone away.

Over the course of the war, key leaders and millions of people around the globe have become more aware of the grim realities of nuclear weapons: even “limited” nuclear use likely would trigger nuclear escalation with global consequences and millions of deaths, nuclear weapon use is immoral and illegal, and nuclear deterrence is unsustainable and ultimately unacceptable.

The Russian invasion of Ukraine has also demonstrated the limitations of nuclear weapons in actual war. U.S. and NATO nuclear weapons have done nothing to help prevent Russian aggression against Ukraine. Instead, Ukraine’s allies have responded with military, political, humanitarian, economic, and diplomatic means to assist with Ukraine’s defense and thwart the aggressor.

Although greater awareness of the dangers of nuclear weapons is very important, it does not, by itself, solve the problem.

Russia might still use a nuclear weapon before the fighting in Ukraine ends. If this spring’s anticipated military offensive-counteroffensives produces another shambolic retreat by Russian forces and Putin fears a humiliating loss of territory and military capacity, he may once again try to resort to nuclear threats or even decide to use nuclear weapons in a desperate, last-ditch attempt to turn the tide.

There are other pathways to escalation. Although U.S. and NATO leaders have made it clear that they do not intend for their military forces to become directly involved in the conflict, the risk of escalation remains very real. A close encounter between NATO and Russian warplanes or an attack by Russia on NATO territory or supply lines, or vice versa, could become a flashpoint for a wider conflict.

The world will remain in a condition of heightened nuclear danger for some time to come.

Given the stakes, civil society and the international community must pursue options to lower tension, increase dialogue, and sustain pressure against those who might break the nuclear taboo. Key objectives include:

Reiterating condemnations of nuclear weapons use: governments: civil society and governments of all stripes need to continue to state unequivocally that nuclear weapons use, or any threat to use nuclear weapons, at any time and under any circumstances, is extremely dangerous and totally unacceptable. Key leaders need to reiterate this message in bilateral meetings, multilateral summits, votes on UN resolutions, and other venues, such as the G-7 Summit in Hiroshima in May and the nuclear Nonproliferation Treaty Preparatory Committee meeting in August. Nuclear war in Ukraine, or anywhere, would affect all people and this risk demands an effective and sustained global response.

Re-establish a regular, high-level U.S.-Russian risk reduction dialogue: Over the long, dangerous course of the nuclear age, the easing of tensions and resolution of crises between the nuclear-armed states has relied not only on good luck and self-restraint, but also effective, leader-to-leader dialogue.

In June 2022, Biden declared that even as he seeks to “rally the world to hold Russia accountable for its brutal and unprovoked war on Ukraine, we must engage Russia on issues of strategic stability.”

While communications bilateral hotlines and U.S. and Russian nuclear risk reduction centers remain in place, they must be used and used effectively. Unfortunately, many diplomatic channels for dialogue between Washington and Moscow on arms control have been suspended since February 2022.

Senior U.S., NATO, and Russian military and political leaders should commit to using direct lines of communication, seek to resume the U.S.-Russian strategic stability dialogue and/or talks on follow-on agreements to the 2010 New Strategic Arms Reduction Treaty (New START), and refrain from provocative actions, such as moving tactical nuclear weapons from storage and toward operational deployment.

Washington and Moscow could consider updating and implementing the aforementioned 1973 U.S.-Soviet agreement requiring the two countries to refrain from nuclear threats and, in times of increased risk of nuclear conflict, “immediately enter into urgent consultations with each other and make every effort to avert this risk.”

Continue to calibrate U.S. and European military support to avoid escalation: The Biden administration has been careful, so far, to design its military aid packages and deliver more advanced weapons to help Ukraine defend itself in a way that does not trigger Russian attacks on U.S. or NATO forces or territory.

The strategy, however, isn’t risk-free. If U.S. and European states begin to supply Ukraine with weapons that can strike deeper into Russian territory, into Russian-controlled Ukrainian territory of Crimea, or into Belarusian territory, such as advanced fighter aircraft or longer-range offensive missiles, and without strict controls on how Ukrainian forces can use these weapons, it may prompt a Russian response that leads to a broader European war.

Continue to refrain from making threats of nuclear retaliationTo date, Biden and leaders of NATO states have warned that Russian nuclear weapons use would certainly lead to catastrophic consequences and escalation but have stopped short of threatening nuclear retaliation. That is wise. Both sides understand that “a nuclear war cannot be won and must never be fought.”

Threats of nuclear retaliation are not only unnecessary and counterproductive, but also would legitimate Putin’s own threats and set red lines no one can afford to cross.

After all, even modern short-range nuclear weapons are devastating and indiscriminate killing machines. Most of the 450 air- and ground-based, short-range nuclear warheads in Russia’s inventory have an explosive yield equivalent to about 10 kilotons of TNT. The bomb that destroyed Hiroshima produced a yield of some 15 kilotons and led to the deaths of an estimated more than 140,000 people within six months of the attack.

The use of nuclear weapons by Russia in Ukraine would also blow apart what support Putin still has from China’s Xi Jinping and India’s Narendra Modi, unleash international wrath, trigger even more dissension to Putin’s rule within Russia, and possibly lead to exactly what he wishes to avoid: direct U.S. or NATO intervention on the side of Ukraine.

Prepare a strong global diplomatic response to further threats of nuclear weapons use: If Russia or any state threatens, let alone uses nuclear weapons, UN member states should pursue a “uniting for peace” resolution to overcome the crippling gridlock in the UN Security Council and authorize effective, collective measures to restore the peace and hold Putin accountable under Chapter VII of the UN Charter. Such a measure would require nearly universal support and unprecedented cooperation from all UN member states to be effective.


The nuclear dimensions of the war on Ukraine underscore the fact that outdated nuclear deterrence policies create unacceptable risks. To eliminate the danger, we must actively reinforce the legal prohibitions and norms against nuclear weapons use and threats of use – as well as their development, testing, possession, and proliferation – and press for effective disarmament diplomacy that leads to concrete action that puts us on the path toward the complete, irreversible, and verifiable elimination of all nuclear weapons.

Such efforts require sustained, smart, and united efforts from the United States, other nuclear-armed states, states allied with nuclear-armed states, as well as the non-nuclear weapon state majority. Our common survival depends on it.

Daryl G. Kimball has been Executive Director of the Arms Control Association (ACA) and publisher and contributor for the organization’s monthly journal, Arms Control Today, since September 2001. 

This blog post was cross-posted by the Arms Control Association as an Issue Brief.

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