Ukraine Nuclear Weapons. What If Ukraine Hadn't Given Up Its Nuclear Weapons? Photo Illustration by Newsweek/Getty Images
Russia's war with Ukraine has escalated into a "nuclear crisis," with far-reaching implications for nuclear deterrence, nonproliferation, disarmament, and the future of peaceful nuclear energy, a leading nuclear expert has warned, telling Newsweek that the conflict, now in its fourth year, might have been prevented had Ukraine retained its Soviet-era nuclear arsenal.
When Did Ukraine Give Up Its Nuclear Weapons?
Ukraine inherited the world's third-largest nuclear arsenal following the collapse of the Soviet Union in 1991. Approximately 30,000 nuclear weapons were spread across Belarus, Kazakhstan, Russia and Ukraine, with Ukraine possessing nearly 1,900 strategic nuclear warheads and thousands of tactical nuclear weapons.
However, three years later, Kyiv chose to denuclearize, signing the Budapest Memorandum and transferring the weapons to Russia. In exchange, Ukraine was promised security assurances from Russia, the U.S. and the United Kingdom.
At the time, Ukraine's decision was widely welcomed, as it helped the country secure financial assistance from the West. But with Russia having openly violated the Budapest Memorandum—first by annexing Crimea from Ukraine in 2014, and by launching a full-scale invasion of the country in 2022—some now question whether Kyiv miscalculated the possible cost of disarmament.
Would a Nuclear Ukraine Have Prevented the War?
In 1993, political scientist John Mearsheimer published commentary titled "The Case for a Ukrainian Nuclear Deterrent," arguing that a nuclear Ukraine was imperative to maintaining peace with its neighbor, Russia. Three decades on, he stands by that position.
"If Ukraine had kept its nuclear weapons, Russia would not have invaded in 2022," Mearsheimer, the R. Wendell Harrison Distinguished Service Professor in the Political Science Department at the University of Chicago, told Newsweek. "Nuclear weapons are the ultimate deterrent."
Mearsheimer said it would have been highly likely that Kyiv would have used its nuclear weapons to defend itself in the event of a Russian invasion, which Ukraine would have viewed as an "existential threat."
"I think the Russians would have recognized that, and therefore would not have invaded in 2022," he said.
"Of course, this is why I argued that it made sense for Ukraine to keep its nuclear weapons, because I thought that in a conventional war, Ukraine stood hardly any chance of defeating the Russians," he added.
Mariana Budjeryn, a senior research associate at Harvard's Belfer Center, and author of Inheriting the Bomb: The Collapse of the USSR and the Nuclear Disarmament of Ukraine, has described the current conflict as being escalated by Russia into a "nuclear crisis" through President Vladimir Putin's constant nuclear threats, signaling and use of intimidation.
Budjeryn agreed with Mearsheimer that a fully developed Ukrainian nuclear deterrent could have dissuaded Russia from launching a large-scale invasion. However, she notes that the presence of nuclear weapons do not entirely eliminate the possibility of conflict.
Border skirmishes and the annexation of Crimea in 2014, might still have happened, Budjeryn said, "but this kind of large scale invasion where the very kind of survival of the country is at stake— that would have been much harder to accomplish, even for a country like Russia that has, measurably, a greater nuclear arsenal than Ukraine."
She also pointed out that a nuclear-armed Ukraine would have forced a stronger and more decisive reaction from the West in 2014 to prevent possible escalation when Putin annexed the Black Sea peninsula of Crimea from Ukraine.
"The reaction of the Obama administration in 2014, which was just a few sanctions and not even a proper slap on the wrist for Russia, would have certainly been more robust and stern [if Ukraine had nuclear weapons] driven by the fears of proliferation," Budjeryn explained.
"Russia would be dissuaded from even starting a large-scale invasion because of the fear that down the road it could escalate to a nuclear threshold," Budjeryn said.
Kyiv's Nuclear Dilemma
Budjeryn challenged the idea that Ukraine simply surrendered its nuclear stockpile.
"Saying that Ukraine inherited the world's third-largest nuclear arsenal and gave it away for nothing is not exactly correct," Budjeryn said*.*
Ukraine's nuclear weapons were designed for Soviet strategic use, meaning what Kyiv inherited was not ready to be used as a nuclear deterrent.
"It wasn't anything it could just grab and quickly turn around and use to deter Russia," she explained.
Ukraine did have options, however, and had the capacity to turn this inheritance down the road into a fully fledged deterrent suitable for its own strategic use, much like Pakistan, North Korea and Iran.
But "that process would have taken time, and it would have taken investment—and time and investment in the early 90s, were the two kind of precious things that Ukraine would struggle to obtain," explained Budjeryn.
"Ukrainian leadership weighed costs and benefits of investing time and resources, and also its capacity to defy the international community, and withstand negative consequences that would have inevitably followed that."
Mearsheimer agreed, noting that in retrospect, there was no strong internal consensus within Ukraine to keep nuclear weapons. The newly independent country was also facing colossal pressure from the U.S. and Russia to give up the nuclear weapons it had inherited from the Soviet Union.
"And given the state of the Ukrainian economy at the time, they didn't have much choice but to abandon those weapons or to turn those weapons back over to Russia."
Could Ukraine Re-Develop Its Nuclear Capabilities?
It's unlikely that Ukraine will redevelop its nuclear capabilities in the near future, Budjeryn said.
"If Ukraine does have money to invest in armaments, that would probably be conventional arms and means of conventional deterrence—longer range [weapons] that could keep Russian important strategic military assets under threat," added Budjeryn.
Mearsheimer also dismissed the idea, adding that Russia would take extreme measures to prevent it from happening.
"With the passage of time, Russia's incentive to make sure Ukraine does not have nuclear weapons has only grown," he said. "You want to remember that back in the early 1990s Russia and Ukraine were not mortal enemies. In fact, relations between the two countries were quite good. But today, nobody would argue that's the case."
"In fact, the opposite is the case…and the hatred on both sides is enormous. There's no way that the Russians would allow Ukraine to acquire nuclear weapons," he added.
How Can Ukraine Defend Against Future Attacks?
As potential peace talks loom, Ukrainian President Volodymyr Zelensky has been urging the West to provide his country with security guarantees.
So far, these requests have been openly rejected by Trump. But U.S. Secretary of State Marco Rubio suggested in an interview with Fox News on February 26 that "what Ukraine really needs is a deterrent…to make it costly for anyone to come after them again in the future."
"And that can be discussed, and it doesn't have to just be America. I mean, the Europeans can be involved in that," said Rubio.
Mearsheimer painted a bleak picture for Ukraine's future, arguing that it has no viable deterrence strategy that Russia would accept.
"This is the principal reason that Ukraine wants a security guarantee from the West," he said. "It understands that it can't deter Russia by itself. It needs a security guarantee from the West, and as Zelensky has made perfectly clear, that has to be a security guarantee from the United States."
The Trump administration has made it clear that Ukraine is not going to get a security guarantee, said Mearsheimer, adding that Russia "would not tolerate that" because "a Western security guarantee is de facto membership in NATO."
Putin has demanded that Ukraine give up its aspirations to join the NATO military alliance.
"The Russians have made it unequivocally clear that Ukraine has to be neutral, and that means no security guarantee from the West, and that means that Ukraine is on its own—and Ukraine on its own, cannot come up with a viable military strategy for containing Russia or deterring Russia in a future conflict or in a future crisis."
Budjeryn, however, sees an alternative. She argues that Ukraine's best defense would be a NATO-style framework—integrating Ukraine's military with European forces to a certain degree.
"Ukraine would have to be bolstered in terms of defense capacity in such a way as to make it prohibitive for Russia to invade again," she said.
She outlined key measures, including joint military development, arms production and intelligence-sharing.
"With the help of European partners and other partners—it's through building up Ukrainian armed forces with Western help," she said.
"It's through all these operational level things that that will have to take shape and essentially integrate Ukraine, to a significant extent, into European and defense architecture," Budjeryn added.
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This story was originally published March 14, 2025 at 5:00 AM.