Between 1945 and 1949, Stalin worked on putting Soviet-friendly governments into Eastern European countries, such as Poland, Romania, Czechoslovakia and Bulgaria. Opponents to the Soviets were arrested and many elections were rigged.
Stalin argued that Russia had been attacked twice by Germany in the twentieth century, so a ‘buffer zone’ around Russia would help to protect them.
Winston Churchill gave a speech in 1946 saying “an Iron Curtain has descended across Europe.” This phrase became commonly used to explain the divide in Europe, between a communist eastern bloc and a capitalist West.