An employee looks at monitors in the control room of the New Safe Confinement metal dome, which was designed and built by French consortium Novarka and encases the reactor at the Chernobyl nuclear plant, on July 10, in Chernobyl, Ukraine. (Sergei Supinsky/AFP/Getty Images)

With HBO’s miniseries Chernobyl, the 1986 nuclear power plant accident in Soviet Ukraine has become a cultural phenomenon, with the entombed reactor now a tourist destination. HBO’s meticulous reconstruction of human folly and the Soviet system’s dysfunction aims to document what happened and why.

The extent of Chernobyl’s geopolitical fallout is less well known. Chernobyl’s effects went well beyond radiation, rippling through the social and political fabric of a deteriorating society. Chernobyl helped to bring down the Soviet Union and constrained independent Ukraine’s nuclear options. It still reverberates today on the front lines of the war in eastern Ukraine and in Moscow’s denials that it is involved in undermining Ukraine’s territorial integrity.

Chernobyl’s fallout contributed to the Soviet Union’s fall.

Chernobyl profoundly shook newly ascended Soviet leader Mikhail Gorbachev. As he wrote in his memoirs, learning about the faulty reactor design led Gorbachev to more deeply distrust the secretive Soviet military-industrial complex, including its much-touted technological prowess and its ability to sustain an arms race with the United States. Chernobyl helped solidify his commitment to arms control — ultimately yielding the landmark Intermediate-Range Nuclear Forces (INF) Treaty in 1987 that eliminated an entire class of nuclear-armed missiles and the Strategic Arms Reduction Treaty (START) in 1991 that cut superpower nuclear forces by nearly half.

But these disarmament policies pitched Gorbachev against the conservatives in Soviet defense establishment. They would stage a coup in August 1991, triggering the Soviet Union’s precipitous unraveling.

The shock of Chernobyl also spurred a strong popular anti-nuclear and anti-establishment sentiment across the USSR. For many Soviet citizens, the causes leading to the disaster, the government’s concealment of its full scope and mishandling of its aftermath encapsulated the Soviet system’s disregard for human life and well-being. In some Soviet republics, popular wrath was mobilized by nascent national movements advocating political independence from Moscow. Scholar Jane Dawson termed the phenomenon “eco-nationalism.”

Nowhere was “anti-nuclear” so synonymous with “anti-Soviet” as in Ukraine, the home of Chernobyl. Galvanized by Chernobyl, Ukraine’s steadfast pull away from Moscow became a major cause of the Soviet empire’s eventual demise.

The trauma of Chernobyl helped push Ukraine to agree to nuclear disarmament.

Ukraine was key in Soviet defense production and military planning, serving as a deployment site for 176 intercontinental ballistic missiles armed with over 1,200 nuclear warheads and 44 strategic bombers carrying over 600 nuclear-tipped cruise missiles. Ukraine hosted the world’s third-largest nuclear arsenal after the United States and Russia.

Yet in July 1990, acting on its anti-nuclear, anti-Soviet stance, Ukraine’s first multi-party parliament passed a Declaration of Sovereignty, announcing that Ukraine intended to become a neutral and non-nuclear state. Ivan Drach, the leader of the pro-independence party Rukh, inserted the non-nuclear clause in the Declaration. In May 2013, as I was researching my doctoral dissertation on Ukraine’s nuclear disarmament after the Soviet collapse, Drach told me his reason for doing so: “It was the Chernobyl mood.”

Just over a year after the Declaration, the Soviet Union was no more and the fate of Soviet strategic arms became a matter of concern and contention.

Ukraine’s nuclear moods shifted, too. Ukrainian leaders now faced the tasks of state building and providing for their country’s security, not knowing whether the new Russia would become a partner or a threat. The rush to disarm dissipated. As relations with Russia soured, a new narrative took hold: As a successor state of the Soviet Union, Ukraine was the rightful inheritor, on a par with Russia, of its nuclear arsenal.

International law was ambiguous. Ukraine was the legal successor to its part of the Soviet Union’s conventional forces. Why not of its nuclear forces as well? Even though Ukraine lacked some key elements of a fully-fledged nuclear weapons program, it had the scientific and technological capability to close the gaps within three to five years. Belarus and Kazakhstan, who also inherited shards of the Soviet strategic arsenal, paid attention to Ukraine’s nuclear gambit.

Had the former Soviet republics kept their nuclear inheritance, the world would have seen the single largest wave of nuclear proliferation in history. Fortunately, such an outcome was averted, in no small part due to the diplomacy of the George H.W. Bush and Bill Clinton administrations that included coercive pressure, technical assistance for denuclearization, and promises of aid and strategic partnership — all aimed at inducing former Soviet republics to renounce nuclear weapons.

In Ukraine, these American policies fell on political soil tilled by the Chernobyl experience. Even among those Ukrainian politicians who were apprehensive of a potential Russian threat, few conceived of using nuclear weapons as a deterrent. Ukraine President Leonid Kravchuk, a high-ranking communist party apparatchik in Kiev during the Chernobyl debacle, was staunchly anti-nuclear. In one interview with a western journalist, Kravchuk betrayed his unease even with a conventionally armed missile: “It is enough to launch one of these missiles into a nuclear power plant — and … catastrophe! … All of us could be obliterated without nuclear arms. Because there are nuclear power stations. Chernobyl. I think all nuclear weapons must be destroyed.”

In Ukraine, they were. In Russia, they were not. The country emerged as the sole nuclear successor of the Soviet Union, while Belarus, Kazakhstan and Ukraine joined the Nuclear Nonproliferation Treaty (NPT) as non-nuclear-weapons states.

To address Ukraine’s security concerns, the United States, Britain, and Russia signed in 1994 the Budapest Memorandum on Security Assurances to Ukraine, pledging to “refrain from the threat or use of force against the territorial integrity or political independence of Ukraine, and that none of their weapons will ever be used against Ukraine except in self-defense.”

Two decades later, Russia launched an intelligence and military operation against Ukraine that resulted in the annexation of Crimea and a war in the Donbas region that has claimed 13,000 lives so far. Whether Russia would have engaged in such actions had Ukraine not given up its nuclear weapons is unanswerable. But it suggests that the Chernobyl legacy may still be felt over 30 years later.

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Mariana Budjeryn, PhD, a research fellow with the Harvard Kennedy School’s Belfer Center and visiting professor at the Peace Research Institute Frankfurt, is writing a book on Ukraine’s nuclear disarmament.