War (15 April – 3 August 1919) fought between the First Hungarian Republic and the Hungarian Soviet Republic and the Kingdom of Romania
The war determined Romanian control of Transylvania and contributed to the fall of the Hungarian Soviet Republic in 1919.
Key Facts
- Start date
- 13 November 1918
- End date
- 3 August 1919
- Duration
- Approx. 9 months
- Romanian forces entered
- Budapest, 3 August 1919
- Key treaty background
- Treaty of Bucharest (1916)
By the Numbers
Location
Cause → Event → Consequence
Following World War I, Hungary's unilateral disarmament under Prime Minister Mihály Károlyi left it vulnerable. Allied plans assigned Romania occupation rights over Transylvania per the 1916 Treaty of Bucharest. Ethnic and political tensions in Transylvania, combined with Romania's desire to secure promised territories, created conditions for armed conflict. The establishment of Béla Kun's Hungarian Soviet Republic further alarmed Allied and Romanian leaders.
From November 1918 to August 1919, Romanian forces advanced into Hungarian territory, crossing demarcation lines established by the Allies. The Hungarian Soviet Republic's Red Army mounted resistance, but Romanian forces ultimately defeated it and occupied Budapest on 3 August 1919. French generals including Foch, Franchet d'Espèrey, and Berthelot supported the Romanian advance, though the Council of Four withheld formal approval.
The Romanian occupation of Budapest on 3 August 1919 effectively ended the Hungarian Soviet Republic. The war settled, in practice, Romanian control over Transylvania and associated territories, presenting the Paris Peace Conference with a territorial fait accompli that shaped subsequent treaty negotiations and the post-war boundaries of Central Europe.
Belligerents & Mobilization Analysis
Side A
1 belligerent
Ferdinand Foch (Allied support), Louis Franchet d'Espèrey (Allied support), Henri Mathias Berthelot (Allied support).
Side B
1 belligerent
Mihály Károlyi, Béla Kun.