The right answer is Soviet Union.
At the end of World War II, the Allied powers divided conquered Germany into four zones, each occupied by either the United States, Great Britain, France, and the Soviet Union (as agreed at the Potsdam Conference). The same was done with Germany's capital city, Berlin. As the relationship between the Soviet Union and the other three Allied powers quickly disintegrated, the cooperative atmosphere of the occupation of Germany turned competitive and aggressive. Although an eventual reunification of Germany had been intended, the new relationship between the Allied powers turned Germany into West versus East, democracy versus Communism. Between 1945 and 1961, some 2.5 million had fled in this way, reducing the GDR’s population by around 15 percent. Ominously for the Communist regime, most emigrants were young and well qualified. The country was losing the cream of its educated professionals and skilled workers at a rate that risked making the Communist state unviable. During the summer of 1961, this exodus reached critical levels. Hence, on that fateful August weekend, the Communists’ vast undertaking to seal off East from West Berlin, to close the ‘escape hatch’.
