In late May , Kun attempted to fulfill his promise to restore Hungary 's borders . The Hungarian Red Army marched northward and reoccupied part of Slovakia . Despite initial military success , however , Kun withdrew his troops about three weeks later when the French threatened to intervene . This concession shook his popular support . Kun then unsuccessfully turned the Hungarian Red Army on the Romanians , who broke through Hungarian lines on July 30 , occupied Budapest , and ousted Kun 's Soviet Republic on August 1 , 1919 . Kun fled first to Vienna and then to the Russian SFSR , where he was executed during Stalin 's purge of foreign communists in the late 1930s
Stalin 's purge
Great Purge
Hungary between the World Wars