Horthy distinguished himself as an admiral in the service of the Dual Monarchy of Austria-Hungary during World War I, in which he defeated the Italian Navy several times. Because of his success, he was promoted to Commander in Chief of the Imperial Fleet in March, 1918, and held that position until he was ordered by the Emperor to surrender the fleet to the new nation of Yugoslavia on October 31.
The end of the war made Hungary a landlocked nation, and hence they had little need for Horthy's services anymore. However, he was still regarded by his people as a war hero, and this status paid off in 1919, when the Communist Bela Kun seized power in the Hungarian capital of Budapest. Horthy organized a force that stormed the city and deposed the Communist government.
In March, 1920, the National Assembly of Hungary proclaimed the country as a monarchy once again, but elected not to recall Charles I from exile. Instead, they proclaimed Horthy as Regent for an indefinite period of time. The admiral without a fleet spent the next 24 years as the de facto King of a country without a coastline.
A staunch conservative, Horthy eventually began to sympathize with Fascism and appointed several pro-Axis officials to cabinet posts in the 1930s. Eventually, when the Nazi government of Adolf Hitler began to rise in power and put pressure on neighboring nations to return territories lost after the war, Horthy became his willing accomplice. In November 1938, the Vienna Arbitrage enabled him to annex nearly one-third of Slovakia. Five months later, when Hitler took over what remained of Czechoslovakia, the Germans allowed Hungary to seize Ruthenia, as well.
In 1940, Hungary prepared to go to war with Romania to regain another lost province, Transylvania. Again, Hitler intervened on his behalf and gave Hungary half of the disputed territory without firing a shot. In May of 1941, Hungary became a full member of the Axis. Before the year was out, the country was at war with the Soviet Union as a German ally.
By 1944, the fortunes of war had turned against Germany and its allies, and the Red Army was approaching Hungary's borders. The Germans intervened in March to appoint a puppet government in Budapest, but Horthy dismissed it in August and began negotiations with the Soviets. Again, the Germans intervened by sending commando Otto Skorzeny to Budapest. Skorzeny kidnapped Horthy's son Nicholas as he went to negotiate with the Soviets, and forced Horthy to abdicate as Regent on October 15.
He spent the rest of the war under house arrest in Germany, treated remarkably well under the circumstances, and was freed by the Russians in May of 1945.
Although Yugoslavia demanded he be tried as a war criminal, the Allies refused to do so. In fact, Horthy served as a prosecution witness in the Nuremberg trials in 1946 and then was released. He settled in Estoril, Portugal, and died there in 1957.
In his will, Horthy asked that his body not be returned to Hungary "until the last Russian soldier has left". His heirs honored the request. In 1993, when the Russians ended 48 years of military occupation of Hungary, Horthy's body was returned and he was buried in his hometown of Kenderes.