At the end of December 2022, I traveled to Ukraine to spend a couple weeks with my mom and celebrate old-calendar Christmas. I had not been back since the war started.

Since Feb. 24, 2022, I have followed the war closely, reading everything I could in reputable and not-so-reputable outlets, countless Twitter threads, and Telegram channels, talking daily with my mom, and staying in touch with Ukrainian colleagues and friends. I told my kids to be good, to mind their grades, and to learn to become more self-sufficient, their mother is off to war with Russia, and plunged into work, sharing what counted as my expertise on the history of Ukraine’s nuclear disarmament and Russian nuclear threats in countless interviews, podcasts, conferences, and articles, in English and Ukrainian. I responded to all requests, from CNN to a Jewish radio station in Pretoria. That, and donating to whatever drives hit my radar was the least I could do, I thought.

The collapse of the Soviet Union in 1991 left its nearly 30,000 nuclear weapons spread over the territories of four newly sovereign states: Belarus, Kazakhstan, the Russian Federation, and Ukraine. This collapse cast a shadow of profound ambiguity over the fate of the world's largest arsenal of the deadliest weapons ever created. In Inheriting the Bomb, Mariana Budjeryn reexamines the history of nuclear predicament caused by the Soviet collapse and the subsequent nuclear disarmament of the non-Russian Soviet successor states.

Although Belarus and Kazakhstan renounced their claim to Soviet nuclear weapons, Ukraine proved to be a difficult case: with its demand for recognition as a lawful successor state of the USSR, a nuclear superpower, the country became a major proliferation concern. And yet by 1994, Ukraine had acceded to the Treaty on the Non-proliferation of Nuclear Weapons (NPT) as a non-nuclear-weapon state and proceeded to transfer its nuclear warheads to Russia, which emerged as the sole nuclear successor of the USSR.

How was this international proliferation crisis averted? Drawing on extensive archival research in the former Soviet Union and the United States, Budjeryn uncovers a fuller and more nuanced narrative of post-Soviet denuclearization. She reconstructs Ukraine's path to nuclear disarmament to understand how its leaders made sense of the nuclear armaments their country inherited. Among the various factors that contributed to Ukraine's nuclear renunciation, including diplomatic pressure from the United States and Russia and domestic economic woes, the NPT stands out as a salient force that provided an international framework for managing the Soviet nuclear collapse.

The Belfer Center’s Project on Managing the Atom, Intelligence Project, and Applied History Project organized a day-long conference in October to mark the 60th anniversary of the Cuban Missile Crisis and to discuss what we’ve learned from the CMC. Managing the Atom’s Mariana Budjeryn discusses the relevance of those lessons for today’s conflict in Ukraine.

While prosecuting its invasion of Ukraine, Russia has relied heavily on nuclear threats, turning the war in Ukraine into a dangerous nuclear crisis with profound implications for the global nuclear order and its two constitutive systems of nuclear deterrence and nuclear restraint. These two interconnected systems, each aiming to manage nuclear possession and reduce the risk of nuclear use, are at once complimentary and contradictory. While tensions between these systems are not new, the war in Ukraine exacerbates them in unprecedented ways. The system of nuclear deterrence seems to be proving its worth by inducing restraint on Russia and NATO, while the system of restraint is undermined by demonstrating what happens to a country not protected by nuclear deterrence. The latter lesson is particularly vivid given Ukraine’s decision to forgo a nuclear option in 1994 in exchange for security assurances from nuclear powers. Russia’s use of nuclear threats as an enabler for escalation and the specter of Russian tactical nuclear use against Ukraine goes well beyond its declared nuclear doctrine. The outcome of the war in Ukraine thus has critical importance for deciding the value of nuclear weapons in global security architecture and for resolving the conundrum between the systems of deterrence and restraint.

One of the most worrying and unprecedented exigencies created by Russia’s invasion of Ukraine is the fate of Zaporizhzhia nuclear power plant, Europe’s largest. Occupied by Russian troops on March 4, the power plant is the repository of an enormous amount of radioactive material, contained in six nuclear reactor cores, spent fuel pools, and dry cask storage. The plant is also the workplace for some 11,000 people. Since taking over, Russia has turned the plant into a military base and used it as a pawn in its war with Ukraine and psychological war with the West.

Former Soviet leader Mikhail S. Gorbachev, who is known for ending the Cold War, dissolving the Soviet Union, and changing the map of Europe, died Tuesday, August 30. He was 91.

We asked several Center experts for their thoughts on Gorbachev and his impacts – and how his life and actions are relevant to the challenges the world faces today.

Today marks three months since Russia invaded Ukraine. For many Ukrainians, that milestone is sinking in. "Now there is a certain plateauing, there's a certain leveling out. On the one hand, you know, the war has entered our everyday reality," Mariana Budjeryn says. "And on the other hand, you're battling the instinct to normalize it." As the war grinds on, how do Ukrainians see things?

Mariana Budjeryn, a Research Associate with the Center's Project on Managing the Atom, is a Ukrainian citizen. She grew up in Lviv, Ukraine, and was there visiting family days before the Russian invasion began. In this video, recorded on May 4, she shares her thoughts and feelings about the war and how her family and friends in Ukraine are doing and thinking about their critical situation.

One of the lingering legacies of the Cold War was the enormous nuclear arsenals amassed by the two superpowers. When one of them, the Soviet Union, disintegrated in 1991, its nearly 30,000 nuclear weapons were located on the territory of not one but four newly sovereign states: Belarus, Kazakhstan, the Russian Federation, and Ukraine. Although command-and-control of Soviet strategic missiles was centralized in Moscow, the specter of the single largest wave of horizontal nuclear proliferation loomed after 1991. By 1994, however, Belarus, Kazakhstan, and Ukraine had decided to join the Nuclear Non-Proliferation Treaty (NPT) as non-nuclear weapons states and to give up the missiles on their soil. Drawing on previously untapped archival records, this article reconstructs the divergent paths of Belarus, Kazakhstan, and Ukraine toward relinquishing their armaments. A combination of domestic and international political factors contributed to the resolution of the problem. Among the various contributing factors, the NPT stands out as a salient force that provided normative framing and guided deliberations on post-Soviet nuclear disarmament.

Although Russia has relied exclusively on conventional weapons for its invasion of Ukraine, behind the scenes lurks Moscow’s massive nuclear arsenal. Hours before Russian forces crossed into Ukraine, Russian President Vladimir Putin reminded the world that his country was “one of the most powerful nuclear states” and that anyone who interfered with his war in Ukraine or threatened Russia directly would face “consequences that you have never faced in your history.” Three days later, as global outrage grew, Putin ordered Russia’s nuclear forces to a higher level of readiness. Even without these explicit threats, Russia’s nuclear deterrent would have prevented Western countries from intervening in Ukraine. Beyond supplying Kyiv with anti-armor and light air defense weapons, they will not come to Ukraine’s defense for fear of nuclear escalation, as U.S. President Joe Biden and other NATO leaders have made abundantly clear. Now that Putin’s attempts to seize Kyiv have been thwarted, there is a risk he will use tactical nuclear weapons to bring Ukraine to its knees. And while this scenario remains unlikely, neither Ukraine nor NATO can do anything to prevent it from happening.

This is a particularly bitter pill to swallow for Ukraine, since it was once home to the world’s third-largest cache of nuclear weapons. After the collapse of the Soviet Union, Ukraine inherited a significant slice of the Kremlin’s nuclear arsenal. But in 1994, the newly independent country decided to surrender that arsenal in exchange for assurances from Russia, the United Kingdom, and the United States that its sovereignty and territorial integrity would be respected. The agreement, known as the Budapest Memorandum, is one that many Ukrainians have come to regret—first in the wake of Russia’s 2014 annexation of Crimea and invasion of eastern Ukraine, and now even more so after its all-out assault on the country. If Ukraine had held on to its arsenal, many have argued, Putin would never have dared to invade the country.