Croatian politician Stjepan Radić was shot on October 1928 and died a month later. Alexander I, King of Yugoslavia, imposed a royal dictatorship in January 1929 and made all political parties illegal. Ante Pavelić left the country for Vienna. He and Gustav Perčec, a former Austro-Hungarian Lieutenant colonel, established contact with organization of Macedonian political emigres. These two groups agreed to coordinate their political activities for achieving full independence for Macedonia and Croatia. There and then, Pavelić secretly met with the leader of outlawed Internal Macedonian Revolutionary Organization (IMRO), Ivan Mikhailov, a declared enemy of Yugoslavia, and made agreement with him to cooperate against the Yugoslav state.
Due to these circumstances, the Court for the Preservation of the State in Belgrade sentenced Pavelić and Perčec to death on 17 July 1929. The exiles started organizing support for their cause among the Croatian emigration in Europe, North America, and South America. The Ustaše organization was small in numbers and was organized in military patterns. They fought Yugoslav statehood by means of terror.
The roots of the Ustaše ideology were in the Croatian nationalism of the nineteenth century. The Ustaše ideological system was chiefly based on the traditional pure Croatian nationalism of Ante Starčević. About it, W. Safran wroteBut another vision of Croatian identity that was closely tied to the Catholic Church and the Vatican and was led by an ex-seminarist Ante Starcevic became the ideological precursor to the Ustase. Starcevic and his followers emphasized the high achievements of Western Catholic, Croatian culture, while Serbian culture was depicted as oriental and inferior. Starčević's racism was further fully elaborated by Ustaša Ivo Pilar [under the pseudonym L. von Südland]. His book was translated into Croatian in 1943, by Pavelić's regime, as one of the tenets of his Ustaše and his Independent State of Croatia. At the same time, the Ustaše borrowed from traditional Croatian nationalism, the National-Socialism of Hitler, the fascism of Mussolini, and even from the program of the Croatian Peasant Party. The Ustaše aimed at an ethnically "pure" Croatia, and saw the Serbs that lived in Croatia and Bosnia and Herzegovina as their biggest obstacle. Along that line, Ustaše ministers Mile Budak, Mirko Puk, and Milovan Žanić declared in May 1941 that the goal of the new Ustaše policy was an ethnically clean Croatia. They also publicly announced the strategy (on July 22, 1941 ) to achieve their goal, which resembled the bloodiest religious wars: "A third must become Catholic, a third must leave the country, and a third must die!"
The Ustaše persecuted the Serbs, who were Orthodox Christians. They were tolerant toward the Bosnian Muslims, claiming that the Muslims were actually ethnic Croats that converted to Islam during the Ottoman Turk occupation of Bosnia. The state even converted a former museum in Zagreb for use as a mosque. The basic principles of the movement were laid out by Pavelić in his 1929 pamphlet "Principles of the Ustaše Movement."
The Ustaše's problem with the Nazi ideology was that the Croats are notSlavs and were considered superior
by Nazi standards. Ustaše ideology thus created a theory about a pseudo-Gothic origin of the Croats in order to raise their standing on the Aryan ladder.
At Janka Puszta training facility in Hungary, IMRO terrorists trained Ustaše operatives in bomb-making and in conspirational activities. The Ustaše put that knowledge to immediate use, carrying out about half-dozen assassinations of Yugoslavian officials or pro-Serb civilians. They carried out a dozen bombings of trains, including the Orient Express, and other public targets during the first four years of their existence. This caused the Yugoslav Government to complain to the League of Nations and forced Hungary to close down Janka Pusta Ustaše training camp. Internal power struggle, and discovery that Perčec's mistress was a Yugoslav police informant, will lead to the Perčec assassination by Pavelić in 1933.
The Ustaše received the most funds from Mussolini, who also supplied this group with an Italian headquarters that changed location whenever Yugoslavia managed to track it down. Camps for training terrorists and saboteurs were set up in Italy, chiefly at Brescia and Borgotaro. An armed insurrection was attempted in 1933, when the Ustaše, armed by the Italians, attempted to invade Yugoslavia by crossing the Adriatic Sea in motorboats. This was unsuccessful, but its lack of success probably was instrumental in the decision to assassinate King Alexander I of Yugoslavia.
Two attempts were made; the last one was successful. Alexander was murdered at Marseilles on 9 October 1934, along with the French Foreign Minister, Louis Barthou. In the wake of the assassination, Mussolini renounced the Ustaše, and the group went deeply underground. The singular lack of armed protection afforded to the Yugoslav king, and the general laxity of security precautions when it was well-known that one attempt had already been made on Alexander's life, are grim tributes to Pavelić organizational abilities. He had apparently been able to bribe a high official in the Surete General. The Prefect of Police of Marseilles, Jouhannaud, was subsequently removed from office.
The assassin was Vlada Georgief Cernozemski, a Bulgarian, who had already killed two members of the Bulgarian Parliament in Sofia. His accomplices were arrested and sentenced to life imprisonment. Pavelic was condemned to death by France, but managed to escape.
Yugoslavia brought charges against Hungary and Italy before the League of Nations in November 1934, offering evidence that Italy and Hungary had openly conspired against her sovereignty. The League of Nations did not discuss the Italian conspiracy against the national sovereignty of Yugoslavia. Moreover, Italy refused to extradite Pavelić and Kvaternik to either France or Yugoslavia, and Hungary bore the brunt of the charges.
After the assassination, the Ustaše activities were prevented completely. A great number of Ustaše were caught and arrested in Italy, Germany, and Hungary. Italy interned many Ustashe to the Lipari camp, where many died. Janka Puszta Ustaše camp was raided by Hungarian police, who arrested some of them. Ustaše from Germany escaped to Switzerland, France, and England.
Widespread outrage at the assassination of Alexander and Barthou led to the first international efforts to combat terrorism since the St. Petersburg Protocol of 1904. The issue was taken up by the League of Nations, which passed the Convention on the Prevention and Punishment of Terrorism in 1937.
After March 1937, when Italy and Yugoslavia signed a friendship treaty, many Ustaše in Italy were extradited to Yugoslavia.
Germany and Italy invaded Yugoslavia on 6 April 1941. On April 10, the most senior home-based Ustaša, Slavko Kvaternik, took control of the police in Zagreb and in a radio broadcast that day proclaimed the formation of the Independent State of Croatia ("Nezavisna Država Hrvatska", NDH). Maček issued a statement that day, calling on all Croatians to cooperate with the new authorities.
Meanwhile, Pavelić and several hundred Ustaše left their camps in Italy for Zagreb, where Pavelić set up his government on 17 April. He accorded himself the title of "Poglavnik", - which was equivalent to "Führer," or "Headman" in English. Pavelić's "Independent State of Croatia" comprised territory of Croatia, Srem, and Bosnia-Herzegovina - except parts of the Dalmatian coast and islands, which were ceded to the Italians. "De facto" control over this territory varied for the majority of the war, as the Partisans grew more successful, while the Germans and Italians increasingly exercised direct control over areas of their interest.