After the collapse of the Austro-Hungarian Empire, Hungary transitioned into a Republic with a very active Communist party. Against a background of popular unrest, in March 1919, the liberal President of Hungary resigned and a Communist coalition came into power. Known as the Hungarian Revolution of 1919, it was a short-lived attempt at a socialist state, led by Béla Kun. The Hungarian Red Army was formed and attempted to win back some of the land lost as a result of World War I. After some military successes, the Communist government became vulnerable internally and the hostility of the Romanian Army led to its downfall a few months later.