International borders dating back decades are currently unravelling. These developments are, variously, the result of irredentist conquest, independence won from empires or larger states, or the reunification of polities previously separated. Some of these border changes have been accomplished relatively peacefully. Others have produced—or have the potential to become—the source of bloody warfare. Allowed to escalate into a worst-case scenario, nuclear exchanges in some of these flashpoints could devolve from a possibility into an imminent threat. 

Fear of annihilation was mostly kept at bay during the Cold War by mutual deterrence, and it retreated to a distant prospect in the years after the Soviet Union broke apart. Suddenly it feels like a pressing concern. Politicians on opposite sides of Poland’s deeply divided politics have both raised the possibility of acquiring nuclear weapons. In early March, Prime Minister Donald Tusk, leader of the Civic Platform Party, told the Polish parliament: “Poland must pursue the most advanced capabilities, including nuclear and modern unconventional weapons. This is a serious race—a race for security, not for war.”

A week later, the Polish president, a member of the opposition Law and Justice Party, said in an interview, “The borders of NATO moved east in 1999, so twenty-six years later there should also be a shift of the NATO infrastructure east. I think it’s not only that the time has come, but that it would be safer if [nuclear] weapons were already here.”

States bordering Russia’s allies are also now considering a nuclear capability of their own. The 160-mile (257 km) frontier between North and South Korea is the most militarised border in the world, but like Poland, South Korea has strictly adhered to a doctrine of non-proliferation until now. But in February, the country’s foreign minister, Cho Tae-yul, told the National Assembly that the possibility of developing nuclear weapons to deter nuclear-armed North Korea is “not off the table.” Cho is speaking to a receptive electorate. The acquisition of nuclear weapons has become broadly popular in the South, which no longer feels secure under the American nuclear umbrella. Cheong Seong-chang, who leads a group of fifty analysts pushing for a domestic nuclear arsenal in South Korea, has said: “We cannot expect—and should not ask—the American president to use his nuclear weapons to defend an ally at the risk of sacrificing his own people. We must defend ourselves with our own.”