Unlike the Western powers that established their colonial empires overseas, Russia created its empire through expansion into adjacent territories. Beginning with its annexation of Kazan in 1552, the Tsarist empire expanded gradually, swallowing up lands it bordered until it extended eastward to Russian North America — now Alaska.

During the early Soviet era, Moscow retained most of the lands it had taken, often by force, as when it crushed independent Ukraine in 1921 and reoccupied the independent Baltic states in 1940.

In the immediate aftermath of World War II the USSR granted nominal independence to the Eastern European states that its forces had occupied during the war.…