At dusk on Kyiv’s Maidan Square, rows of flags and portraits mark the dead; a few steps away, Ukrainian men, women and children dance. Walking there in mid-September, I saw loss and hope share the same space.

That coexistence is a policy lesson: Ukraine’s fate and Europe’s security are inseparable. This month, Russian drones crossed into NATO airspace over Poland; days later, three Russian MiG-31s violated Estonian airspace over the Gulf of Finland before turning back. No one was hurt, but the war has entered the alliance’s airspace and the risk of miscalculation has grown.

Deterrence now turns on clarity. Baltic Air Policing, a peacetime mission in which NATO Allies deploy fighter jets to cover the airspace of Estonia, Latvia and Lithuania, was built decades ago for an era when violations were rare and mostly theatrical. It no longer fits — the scale and brazenness of Russian behavior make that plain.