On June 1, 1996, two trains arrived in Russia transporting the last nuclear warheads that had been deployed in Ukraine when the Soviet Union collapsed. That concluded the process in which Kyiv gave up what was then the world’s third-largest nuclear weapons arsenal—exceeding Britain, France, and China combined. The Ukrainian government did so in large part because of Russia’s assurances that it would respect Ukraine’s sovereignty and territorial integrity, and refrain from the use of force against Ukraine.

Twenty-six years later, Russia is more than three months into a massive invasion of Ukraine. This has understandably led Ukrainians to question the wisdom of giving up those nuclear arms, and Vladimir Putin’s war has dealt a blow to future efforts to arrest nuclear proliferation.

Read the rest at the Bulletin of the Atomic Scientists