There are several Miklós Horthys, starting with the commander-in-chief of the National Army, followed by the much idealized His Serene Highness, and finally the man who ended up making weighty political decisions for which he was ill equipped.
I'm most familiar with the early Miklós Horthy whose name, despite revisionist efforts of late, is inseparable from the White Terror that followed the collapse of the Hungarian Soviet Republic.
Horthy was not well known before 1919. He was a high-ranking officer in the Austro-Hungarian navy, but his job came to an end with the collapse of the dual monarchy. Because he had inherited about 350 hectares of land in Kondoros he retired to lead the life of a Hungarian landowner of modest means. But then, according to his memoirs, he received word from Count Gyula Károlyi who was organizing a "national government" in Arad (in Romania today) that was supposed to be ready if and when the Hungarian Soviet Republic of Béla Kun fell. Almost at the same time he received a call from István Bethlen who was organizing the Anti-Bolshevik Committee (ABC) in Vienna. They needed a man to head the ministry of defense.
Horthy obliged and joined Károlyi's government that in the interim had moved on to Szeged, then under French occupation. It was not much of a government: in three months there were three different governments and many of the posts were not filled at all. However, Horthy served all through. His army grew steadily because of the unemployed former army officers who came to Szeged in hope of employment and who were full of a desire to battle the communists. Their anti-communism unfortunately wasn't coupled with democratic impulses. For the most part their political views tended toward the far right. For example, among them was Gyula Gömbös who in the thirties became prime minister. Most historians agree that Gömbös's plans for Hungary bore a suspicious resemblance to the ideas of Mussolini. I devoted a couple of posts earlier to the uncanny resemblance between the political ideas of Gyula Gömbös and Viktor Orbán.
Horthy was a babe-in-arms when it came to politics even in the late thirties, after almost twenty years as governor of Hungary. In the summer of 1919 he really must have been at a loss. We know from people who were acquainted with him that he was easily influenced. The young officers who surrounded him in Szeged were not just ordinary anti-communists but far-right anti-semites who had an impact on Horthy's conservatism. Especially since they began building a cult of personality around him already in Szeged. And, as we know, human nature is such that people can easily fall prey to vanity. Ignác Romsics in an article about Horthy quotes from Szeged papers in which they refer to him as an extraordinary leader whose men are ready to follow him to the end of the world.
Unfortunately, he often talked irresponsibly, and the young far-right officers–who later proudly called themselves the first Nazis–took his words seriously. Why shouldn't they when, for example, he swore in public that he would hang from the first lamp post all those Jews who stole public funds? In the same speech Horthy mentioned by name the editor-in-chief of Népszava as a target. And, behold, a few months later in February 1920 the editor-in-chief of Népszava, Béla Somogyi, and his young colleague, Béla Bacsó, were killed by Horthy's men. As for the "white terror" that was introduced after Horthy and his national army received permission from the French military in Szeged to cross the demarcation line into Transdanubia, he himself gave permission to Pál Prónay, one of his officers, to do a thorough "cleaning job." Accordingly, Prónay and his men moved from village to village, inquiring from the locals who was involved in the local workers' councils and who the leaders were during the Soviet period, and without further ado hanged them. Not on lamp posts because I gather that most of those villages didn't have electricity, but on trees! And while they were at it they took pictures.
The White Terror. Horthy's bad reputation in the 1920s had a lot to do with it. The number of victims until recently was estimated to be 2,000, a number I always found too high. Hungarian historians in the 1970s and 1980s rather irresponsibly kept repeating this magic number that came from a contemporary Austrian left-wing paper. Lately historians discovered that László Fényes, a left-wing journalist, at the request of Népszava made a serious effort to collect details on the victims and came up with 646 names. On the basis of this partial figure Romsics estimates that the real number was close to 1,000. By way of comparison, in the Horthy regime an effort was made to put together a list of the victims of the Red Terror and they came up with a number between 300 and 400.
As for the murder of Somogyi and Bacsó, "Horthy's responsibility is unquestionable," says Romsics in the above mentioned article. He and other historians base that opinion on the testimony of Ödön Beniczky, minister of interior at the time the murders took place. In 1925 he made it clear that he knew who committed the murders and wanted to prosecute, but Miklós Horthy intervened. As a result, Beniczky had to resign. After he testified before a military court, his testimony was made public in a newspaper. Because after Horthy became governor his person became "inviolable," meaning he couldn't be publicly criticized, especially accused of a crime, Beniczky was prosecuted and sentenced to three years in jail. In the thirties he committed suicide.
In any case, in November 1921 Horthy gave amnesty to all those who "because of their national enthusiasm, in the interest of the nation committed certain acts." I might add that one of the murderers of Somogyi and Bacsó and an allegedly faithful follower of Horthy, Emil Kovarcz, years later became a member of the Arrow Cross Party and in that capacity was the leader of an attack on the famous synagogue in downtown Budapest. He was arrested and sentenced but while waiting for appeal he escaped to Germany only to return after the German occupation of Hungary. It was in his apartment that plans for a military takeover were hatched that removed his "beloved Miklós Horthy" on October 15, 1944.
I might add a footnote here. In 2008 the city council of the eighth district had a brilliant idea. They wanted to change the name of Béla Somogyi Street to Emil Kovarcz Street. Poor Béla Bacsó had been already stripped of his right to have a Hungarian street named after him. As far as I know the city fathers eventually saw the light. After all, someone who was found guilty of war crimes and hanged in 1945 should not be honored by having a street named after him, especially not the street that previously bore the name of the man he murdered.