Károlyi informed the cabinet that only the Hungarian Social Democratic Party could possibly form a new government. Unknown to Károlyi, however, the Social Democrats had merged with the Hungarian Communist Party; the latter promised that the Russian SFSR would help Hungary to restore its original borders. Although the Social Democrats held a majority in the newly merged Hungarian Socialist Party, the communists led by Béla Kun immediately seized control and announced the establishment of the Hungarian Soviet Republic on 21 March 1919.