Opening a textile factory, he distinguished himself as a successful businessman and an active member of the country's Croatian émigré community, co-founding several cultural societies and publications.

[2] In the years leading up to the Axis invasion of Yugoslavia, Rojnica served as an agent of the Abwehr, Germany's military intelligence service,[3] where he received the code name "Ante".

The same day, local Ustaše launched a campaign of arrests, killings and expulsions targeting the movement's ideological opponents, such as members of the Communist Party of Yugoslavia.

[9] He was succeeded by Vlado Herceg, who had previously served as a warrant officer in the Poglavnik's Bodyguard Brigade (Croatian: Poglavnikova tjelesna bojna), which was tasked with guarding Pavelić.

[11] In the war's final months, Rojnica extorted refugees passing through Dubrovnik, forcing them to pay him exorbitant sums in return for safe passage.

[2] In late March or early April 1947,[b] Rojnica landed in Argentina as a stowaway aboard the passenger ship Maria C.[c] His escape had been facilitated by the Ustaše functionary and Roman Catholic priest Krunoslav Draganović, one of the main organizers of the network of ratlines smuggling fascist war crimes suspects out of Europe.

On 31 August 1951, he was granted Argentine citizenship under the false name he had used to enter the country, and on 20 December 1954, he successfully petitioned the government to legally change his name to Juan Rojnica.

[d] Referring to anti-Semitic atrocities, Rojnica stated that "Croats are not guilty for the fate of the Jews," and maintained that the Germans were solely responsible for The Holocaust in Croatia.

Rojnica was a close associate of Carlos Menem, who served as the President of Argentina between 1989 and 1999, and exploited this relationship to illegally procure Argentine arms for Croatia.

[24][e] United Nations Security Council Resolution 713, passed on 25 September 1991, had imposed an international arms embargo on Yugoslavia and its constituent republics.

[24] On 16 January 1992, Menem met with a delegation of Croat émigrés headed by Rojnica at Quinta de Olivos and announced that Argentina would recognize Croatia's declaration of independence from Yugoslavia—the first Latin American country to do so.

[26] Several weeks later, a representative of the Simon Wiesenthal Center met with Argentine officials demanding Rojnica's arrest, noting that his name figured prominently in a list of eighteen war crimes suspects alleged to be hiding in Argentina that the organization had given to the country's Minister of the Interior, José Luis Manzano.

[12] The case gained widespread attention that August when the Croatian weekly Feral Tribune published a copy of the anti-Semitic and anti-Serb decree that Rojnica had issued in Dubrovnik in June 1941.

Frane Franić, Archbishop of the Roman Catholic Archdiocese of Split-Makarska, praised him as "a deeply religious man" who "deserves the highest Croatian medals".

[8] Amid widespread public criticism, the President of Croatia, Franjo Tuđman, ultimately reversed his decision, but never issued a formal apology.

"[14] He blamed "enemies of the Croatian state" for his dismissal, saying that the Feral Tribune had "set him up", targeted him for "public defamation" and "forced the president into such action".

[32] In March 1997, Menem acceded to a request from the Simon Wiesenthal Center to hand over the bank records of 334 Nazi officials and their wives and mistresses who had fled to Argentina after the war; Rojnica's name was absent from the files.

The Argentine press attributed Rojnica's apparent immunity to the sizeable financial contributions former Ustaše members had made to Menem's electoral campaigns.

Rojnica became the subject of renewed media scrutiny in May 1998, following the widely publicized arrest of former Jasenovac commander Dinko Šakić, who had also settled in Argentina after the war.

In an interview with La Nación that month, Rojnica admitted to serving as the Ustaše commissioner of Dubrovnik, but dismissed the war crimes allegations against him, calling them "a big lie invented by the Serbs and by the communists", and adding, "I am a hero of Croatia!

[34] In 2001, the director of the Simon Wiesenthal Center's Jerusalem office, Efraim Zuroff, listed Rojnica among eight "major Nazi war criminals" still at large.

[36] The following year, he criticized the Serbian authorities for failing to issue arrest warrants for Rojnica and two other Axis war crimes suspects—the Croatian Milivoj Ašner and the Hungarian Sándor Képíró.