The Hungarian Revolution of 1956 was a spontaneous nationwide revolt against the Communist government of Hungary and its Soviet-imposed policies, lasting from October 23 until November 10, 1956. It began as a student demonstration which attracted thousands as it marched through central Budapest to the Parliament building. A student delegation entering the radio building in an attempt to broadcast their demands was detained. When the delegation's release was demanded by the demonstrators outside, they were fired upon by the State Security Police (ÁVH) from within the building. The news spread quickly and disorder and violence erupted throughout the capital.
The revolt spread quickly across Hungary, and the government fell. Thousands organized into militias, battling the State Security Police (ÁVH) and Soviet troops. Pro-Soviet communists and ÁVH members were often executed or imprisoned, as former prisoners were released and armed. Impromptu councils wrested municipal control from the communist party, and demanded political changes. The new government formally disbanded the ÁVH, declared its intention to withdraw from the Warsaw Pact and pledged to re-establish free elections. By the end of October, fighting had almost stopped and a sense of normality began to return.
After announcing a willingness to negotiate a withdrawal of Soviet forces, the Politburo changed its mind and moved to crush the revolution. On November 4, a large Soviet force invaded Budapest, killing thousands of civilians. Organized resistance ceased by November 10, and mass arrests began. An estimated 200,000 Hungarians fled as refugees. By January 1957, the new Soviet-installed government had suppressed all public opposition. These Soviet actions alienated many Western Marxists, yet strengthened Soviet control over Central Europe, cultivating the perception that communism was both irreversible and monolithic.
Public discussion about this revolution was suppressed in Hungary for over 30 years, but since the thaw of the 1980s it has been a subject of intense study and debate. At the inauguration of the Third Hungarian Republic in 1989, October 23 was declared a national holiday.
Source:
http://en.wikipedia.org/wiki/Hungarian_Revolution_of_1956