Charles I of Austria's attempts to retake the throne of Hungary

After Miklós Horthy was chosen Regent of Hungary on 1 March 1920, Charles I of Austria, who had also reigned as Charles IV of Hungary, returned to Hungary twice, to try unsuccessfully to retake his throne. His attempts are also called the "First" and "Second Royal coups d'état" (első és második királypuccs in Hungarian) respectively.

On 13 November 1918, Charles issued a proclamation in which he relinquished his right to take part in Hungarian affairs of state. He also released the officials in the Hungarian half of the empire from their oath of loyalty to him. This came two days after he issued a similar statement withdrawing from Austrian politics. Although these statements have been described as abdications, Charles deliberately avoided using that term in the event the people of either nation recalled him.

Charles's last Hungarian prime minister, Mihály Károlyi, took advantage of the situation and proclaimed the Hungarian Democratic Republic, with himself as provisional president. The continued Allied occupation made Károlyi's situation untenable, and in March 1919 he was pushed out of office by a Social Democratic-Communist coalition that made Hungary a Soviet republic. Under the Communist leader Bela Kun, Hungary became the world's second Communist nation. However, Kun's harsh rule alienated large numbers of people, and he was overthrown in August. Eventually, Archduke Joseph August took power as regent for Charles, only to be forced out when the Allies refused to recognize him.

Finally, in March 1920, Miklós Horthy, the last commander of the Austro-Hungarian Navy, was named regent of Hungary.

The former king's first coup attempt began on 26 March 1921. This was Holy Saturday that year: the diet was not in session, the diplomatic corps was away in the country, and Regent Horthy planned a quiet holiday with his family in the royal palace. Charles, prompted by suggestions from his immediate Swiss entourage and trusting in the promises of certain European royalist circles, took advantage of this quiet. Despite warnings by many of his supporters and by Horthy himself that the time was not right to return to the throne, he was optimistic, believing that the mere news of his reappearance and Horthy's willingness to hand over power would revive Hungarians' love for their king. His secret negotiations with French Prime Minister Aristide Briand led him to expect French support if he succeeded, and no armed intervention from Hungary's neighbours.

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Wikipedia