The answer to the blank is: East Germany.
After the fall of Germany in WWII, the winning forces of the war split the German territory and the Soviets gained control over the eastern section of this country, with East Berlin being the capital of this territory. East Germany, or German Democratic Republic (GDR), became part of the Eastern Bloc (dominated by the Soviet Union) from 1949 to 1990 (this latter date marked by the fall of the Berlin Wall).
