The United States estimates Russia has a stockpile of up to 2,000 tactical nuclear warheads, some small enough they fit in an artillery shell. But the detonation of any tactical nuclear weapon would be an unprecedented test of the dogma of deterrence, a theory that has underwritten America’s military policy for the past 70 years. Possessing nuclear weapons isn’t about winning a nuclear war, the theory goes; it’s about preventing one. If Mr. Putin dropped a nuclear weapon on Ukraine — a nonnuclear nation that’s not covered by anyone’s nuclear umbrella — what then? Many in the administration believed the Kremlin’s dirty bomb ploy posed the greatest risk of nuclear war since the 1962 Cuban missile crisis.

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Persons: Putin, Sergei Shoigu, Lloyd Austin, Russia Sergei Shoigu, Britain Ben Wallace, Defense Turkey Hulusi Akar, Sebastien Lecornu, General Austin, Mark Milley, Biden, Putin’s, William J, Burns Organizations: United, of American, NATO, Defense, State, Defense Turkey, National Defense, Defense Minister American, Russian, Biden, Joint Chiefs, Staff, Moscow, White House, State Department, The Energy Department, Strategic Command, ’, Pentagon, Unmute Defense, Central Intelligence Agency Locations: Washington, Ukraine, Russia, United States, Kharkiv, Kherson, Russian, U.S, Crimean, Moscow, Poland, China, India, Turkey