It prevented an attempt by Ustasha emigrants to carry out terrorist and diversionary actions in Yugoslavia and unite anti-communist Crusaders in the country, in an uprising against the new authorities.
Infiltration of the Ustashas (called Operation April 10[note 1]) was initiated with the consent of Ante Pavelić (after its failure, he distanced himself from it).
A total of 96 Ustashas were arrested, killed, or executed including former concentration camp commandants Ante Vrban and Ljubo Miloš.
[1] With the defeat of the Independent State of Croatia and the withdrawal of its army in Austria in May 1945, scattered groups of soldiers in Yugoslavia escaped capture.
Croatian emigrants abroad spread exaggerated news about the number of crusaders and their struggle against Yugoslav security forces.
Kavran accepted their participation with disbelief, since the Ustashas in Italy were under the strong influence of Ante Moškov, who was in conflict with Pavelić.
Prior to the start of the operation, the bureau for Croatia in Zagreb in May received a communication from Vienna from his main agent among the Ustasha emigrants that the first group would come to Papuk soon.
UDBA immediately prepared a response under the secret name Gvardijan,[note 2] Kavran's nom de guerre, and set traps.
After a few days of wandering through Papuk, Dilje, Psunj and Babja Gora, they were convinced that no crusader groups were to be found and returned to Austria.
He sent Kavran a false message, informing him that the first group on Papuk had been linked to the crusaders, and stressed that no officers were present.
Upon their arrival, UDBA learned from the peasants in the vicinity of Koprivnica and Đurđevac that they had met five suspected rebels.
In the meantime, Miloš stated that as commander of Jasenovac concentration camp, he was responsible for war crimes and agreed to collaborate with UDBA.
Due to worsening Yugoslav-Soviet relations after Tito-Stalin split, UDBA feared that further operation would be in danger, as Soviet intelligence service might knew for infiltration of former Ustasas, and might use as propaganda tool against Yugoslavia.
UDBA lured him by sending him false message requesting his arrival, otherwise his men would run resistance without Kavran's control.