Like Stalin, Putin thinks nations can be defined objectively, and he has declared there is no Ukrainian nation separate from the Russian one. History matters for national identity, but sometimes serves as a tool for aggressive nationalism. Contemporary Ukraine was born in 1991. During that year there were negotiations over a union treaty to replace the Union of Soviet Socialist Republics with a new Union of Sovereign States. In August, hardliners attempted a coup to preserve the existing state. After they were defeated, the Ukrainian parliament declared independence and this act was overwhelmingly supported across Ukraine in a referendum on...