Louis Franchet d'Espèrey in the context of Fifth Army (France)

The Hungarian–Romanian War (Hungarian: magyar–román háború; Romanian: Războiul Româno-Ungar) was fought between Hungary and Romania from 13 November 1918 to 3 August 1919. The conflict had a complex background, with often contradictory motivations for the parties involved.

After the unilateral self-disarmament of the Hungarian army by the pacifist Hungarian prime minister Count Mihály Károlyi, the Allies of World War I intended that Romania's Army, the Czechoslovak army and the Franco-Serbian armies to occupy various parts of Kingdom of Hungary. At the same time, there was a reluctance to allow Romania to occupy Hungary fully, although their intention was to, at least in part, satisfy the Romanian claims in accordance with the Treaty of Bucharest (1916) which proposed that Hungary cede Transylvania, Partium and parts of Banat to Romania. The situation was further complicated by the strained relationship between the Romanian delegation at the Paris Peace Conference and the Great Powers. France, in particular, was keen on the participation of Romania in the intervention against the Bolshevik forces in Russia while the Romanian authorities conditioned this involvement on the fulfillment of the promises made by the Allies in 1916. Some Allied leaders in Paris supported the advance of the Romanian Army while the Council of Four withheld its approval of the military actions. The French General Staff encouraged a continued Romanian advance to Budapest, with Generals Ferdinand Foch, Louis Franchet d'Espèrey, and Henri Mathias Berthelot particularly in favor of this approach.