The Hungarian Revolutionary War was a conflict between Czechoslovakia, Romania, and Soviet Hungary, shortly after the end of World War I which lasted from March 28, 1919 to June 4, 1920.
With the volatile and politically unstable atmosphere of Central Europe in the inter-war years, the establishment of independent governments of the former Austria-Hungarian Empire in November 1918 would see the struggle to regain territories of the former empire.
However, Hungarian Prime Minister MihA ly KA rolyi resigned within four months (on March 20, 1919) in favor of BACla Kun, a pro-Bolshevik who had been sent by Lenin, quickly seizing power and establishing a dictatorship. Appealing to Hungarians with promises of liberating the provinces lost to neighboring countries in the Treaty of Versailles, within a week of his rise to power, Kun declared war upon Czechoslovakia as Hungarian forces invaded the province of Slovakia on March 28 capturing southern Slovakia within weeks. Czechoslovakian forces were unable to recapture occupied parts of Slovakia. Despite Kun's assurances of Russian support, the Allies began to put pressure on the Hungarian government and, within three weeks, Hungary was forced to withdraw from Slovakia after given an ultimatum from France.
Despite the setback, Hungary continued in its campaign to reestablish Hungary's pre-1914 borders as Kun, desperate to regain the loss of public support, threatened an invasion of Transylvania. However, Romania launched a pre-emptive strike on April 10 which, due to anti-Communist revolts, quickly advanced towards Budapest. The Romanians captured the capital on August 4, only three days before Kun's escape to Vienna.