In 1956, citizens of Hungary began to protest for their lack of freedom; this led to riots in the Capital, Budapest. Police forces of Hungary tried to prevent these riots.
Krushchev sent the Red Army into Hungary to restore order. He placed communist dictator Rakosi with more liberal Imre Nagy. the Red Army then eventually withdrew.
By the end of October 1956, Nagy announced a set of proposed reforms including leaving the Warsaw Pact and eventually becoming a neutral country. Following from this, Kreshchev was concerned that the break of Hungary leaving the Warsaw Pact would influence other countries to follow.
Kreshchev ordered a soviet invasion on Hungary. Supporters of Nagy fought against this and begged the West for support, however, none came.
A new communist government was set up that supported the communist ideologies, which lead to the chain of events of Nagy being executed.
Nagy and many of his supporters had believed that Kreshchev's criticism of Stalin would lead to a softer approach with the satellite countries. However, they miscalculated.