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, Kavran's
nom de guerre, and set traps. Kavran, with the support of other emigrant leadership, sent his first group. He chose former Ustasha mayor Ljubo Miloš (former commander of the
Jasenovac concentration camp), mayor Ante Vrban and Luka Grgić. Kavran assured them that they would find supporters of the
Croatian Peasant Party. Their task was to organize and connect these groups. On 7 June, the group crossed the Yugoslav-Hungarian border. Miloš sent a message to Kavran that no crusader group was in the
Koprivnica area and that they would go further. 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. Upon their return on 19 July, they met a UDBA agent who connected with the group, and reported to them about his station. He presented himself as a member of a crusader group of major Mikulčić (whom they personally knew), so they arranged a meeting with him. Miloš and Vrban started with UDBA members in an improvised camp. While they were resting, the UDBA officer uttered a signal that read "Jozo, bring me water", members of UDBA threw themselves at Miloš and Vrban. Grgić was liquidated later. Vrban and Miloš were transferred to the prison on Savska cesta in Zagreb. Both explained the plans of their colleagues. The Croatian section of UDBA, under the direction of Ivan Krajačić, went into action. 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. The goal was to capture senior officers and prominent politicians. Kavran sent another group from Austria that crossed Yugoslav-Hungarian border on 20 July. Upon their arrival, UDBA learned from the peasants in the vicinity of
Koprivnica and
Đurđevac that they had met five suspected rebels. The group was arrested in
Suhopolje on 29 July. In the meantime, Miloš stated that as commander of
Jasenovac concentration camp, he was responsible for war crimes and agreed to collaborate with UDBA. He gave the code and radio signals and signed written messages. In the following months, group after group fell into UDBA traps. Route through Hungary was cut, when Hungarian arrested one guides who lead Ustasha through Yugoslav-Hungarian border. So, UDBA arranged new line for infiltration of Ustasahas via Slovenia. Capture of infiltrated groups was continued until summer. 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. Yugoslavs were certain that Pavelić has left Europe and that he would not return in Yugoslavia, so main objective became Kavran. UDBA lured him by sending him false message requesting his arrival, otherwise his men would run resistance without Kavran's control. The last group on July 3 included Kavran himself, who was immediately arrested. Kavran's arrest ended Operation Gvardijan. On 9 or 10 July 1947, UDBA sent a dispatch to the Ustasha base in
Villach, Austria: "We've fucked you over. Full stop. All of your men are in our prisons." All 96 infiltrators were arrested or killed. In 1948, the courts of the People's Republic of Croatia sentenced 20 of them (including Miloš, Vrban and Kavran) to death by hanging and permanent loss of all rights and 57 to death by shooting, while others were sentenced to life imprisonment or imprisonment ranging from 15 to 20 years. Together with this group was a group composed of former Colonel of Maček's Croatian Peasant Defense and two former
Chetniks. Those three men were gathered in
Trieste by former Chetnik Lieutenant Colonel Siniša Ocokoljić. They infiltrated Yugoslavia via the
Adriatic Sea, but were arrested. == List of captured in Operation Gvardijan ==