Warsaw Pact:

In 1956, following the declaration of the Imre Nagy government of withdrawal of Hungary from the Warsaw Pact, Soviet troops entered the country and removed the government. Soviet forces crushed the nationwide revolt, leading to the death of an estimated 2,500 Hungarian citizens.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". In which year did Hungary attempt to leave the Warsaw Pact?
1956