CNN  —  Russia’s use of a nuclear-capable ballistic missile on Thursday is the latest escalation in the Ukraine war. It also marks a decisive, and potentially dangerous moment in Moscow’s conflict with the West. The use of what Vladimir Putin said was a ballistic missile with multiple warheads in offensive combat is a clear departure from decades of the Cold War doctrine of deterrence. Ballistic missiles with multiple warheads, known as “multiple independently targeted reentry vehicles,” or