text: Revolutions and counter-revolution The First World War brought about the dissolution of Austria-Hungary in 1918. The Aster Revolutiona movement of the left-liberal Party of Independence, the Social Democratic Party and the Radical Citizens' Partypersuaded Charles IV (), to appoint the radical Count Mihály Károlyi (d. 1955), prime minister on 31 October. After the Lower House dissolved itself, Hungary was proclaimed a republic on 16 November. The Hungarian National Council adopted a land reform setting the maximum size of the estates at  and ordering the distribution of any excess among the local peasantry. Károlyi, whose inherited domains had been mortgaged to banks, was the first to implement the reform.
  The Allied Powers authorized Romania to occupy new territories and ordered the withdrawal of the Royal Hungarian Army almost as far as the Tisza on 26 February 1919. Károlyi resigned and the Hungarian Communist Party leader Béla Kun (d. 1938) announced the establishment of the Hungarian Soviet Republic on 21 March. All estates of over  and all private companies employing more than 20 workers were nationalized. The Bolsheviks could not stop the Romanian invasion and their leaders fled from Hungary on 1 August. After a short-lived temporary government, the industrialist István Friedrich (d. 1951) formed a coalition government with the support of the Allied Powers on 6 August. The Bolsheviks' nationalization program was abolished. The Hungarian Social Democratic Party boycotted the general elections in early 1920. The new one-chamber Diet of Hungary restored the Hungarian monarchy, but without restoring the Habsburgs. Instead, a Calvinist nobleman, Miklós Horthy (d. 1957), was elected regent on 1 March 1920. Hungary had to acknowledge the loss of more than two thirds of its territory and more than 60 percent of its population (including one third of the ethnic Hungarians) in the Treaty of Trianon on 4 June.