The perception of communism in the US was shaped by the Cold War, which began after World War II when the Soviet Union failed to uphold the commitments it made at the Yalta Conference. Instead of holding elections for new governments, as agreed at Yalta, the Soviet Union occupied several Eastern European countries, leading to a strained relationship with the US. Subsequent international events served to increase the apparent danger that communism posed to Americans: the Stalinist threats in the Greek Civil War (1946–1949); the Czechoslovak coup d'état of 1948; and the 1948 blockade of Berlin.[11]