When the people of Ukraine rose up against an authoritarian president and peacefully occupied Kiev's main square, they made the Euromaidan synonymous with moral courage and the yearning for freedom. But Vladimir Putin, sensing an existential threat to his own rule in Moscow, struck back.

Employing a noxious brew of mercenaries, local agents of influence, fake news on steroids, and disguised Russian special forces, Putin invaded Ukraine, seizing Crimea and creating a phony separatist movement to set against Kiev. Complete with all the trappings of statehood, with its own flag and armed...