ALL of these events happen in 1956:
Stalin dies, 'de-Stalinisation' is hope to occur and Rakosi (the Stalinist leader of the Hungarian communist party) falls from power in July. During October, students, workers and soldiers attack the secret police. Imre Nagy (a 'westiniser') becomes prime minister on 24th October . Russian army leaves Hungary on 28th October. November 3rd, Nagy said that Hungary would leave the Warsaw Pact, which Khruschev does not agree with. So on 4th November, the Soviet Union invades Hungary and destroys the Hungarian army. About 4,000 Hungarians are killed in total. Janos Kadar, a Russian supporter, replaces Nagy, who is executed. The Hungarians looked to the USA for help as they had promised to support countries fighting against communism in the Truman Doctrine(1947) but the USA did nothing.The force of the Soviet army against the Hungarians disgusted the USA, but they could do nothing as they had more important problems at the time (e.g. the Suez Crisis and the Vietnam War), and could not risk nuclear war for one country's sake. This caused tensions to rise between the USA and the Soviet Union as the USA saw how much willing the Soviet Union was to uphold communisn in the USSR.
