Frank gained prominence as a member of the group that tore down a Hungarian flag to protest the 1895 visit by Emperor Franz Joseph to Zagreb.

Before the dissolution of Austria-Hungary, Frank advocated for trialist reform of the empire as a means of protection against the Magyarisation and Serbian irredentism.

Frank sought a political alliance with Gabriele D'Annunzio, who had seized the city of Rijeka (Fiume) in the immediate aftermath of World War I for the Italians.

Subsequently, Frank focused on gaining Hungarian support by advocating for a revised version of the Treaty of Trianon, which partitioned the Kingdom of Hungary after the war.

Frank was a part of the delegation of Croatian politicians to Emperor Charles I of Austria and prime minister István Tisza in the final year of the war.

They unsuccessfully tried to persuade the emperor to reform Austria-Hungary according to trialist ideas, which would give Croats greater political autonomy within the empire.

[5] As Austria-Hungary disintegrated, and its South-Slavic population largely became ruled by the newly established Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia), Frank came into conflict with the new authorities as an opponent of Yugoslavist ideas.

[1] Frank moved to Graz, Republic of German-Austria in 1919[5] where he became a prominent figure among Croatian political émigrés, largely consisting of former Austro-Hungarian Army officers.

[1] Historian Jozo Tomasevich described Frank as the only person of significant standing in Croatian political emigration in the aftermath of World War I.

[7] Frank sought support from Gabriele D'Annunzio who had seized the city of Rijeka (Fiume) in the immediate aftermath of World War I and established the Italian Regency of Carnaro.

The first agreement promised D'Annunzio's support of Croatian, as well as Albanian and Montenegrin, émigrés in the form of supplying money and arms for the struggle against the Kingdom of Serbs, Croats and Slovenes.

Frank handed his copy to the Italian ambassador to Hungary, while Pavelić passed his to Roberto Forges Davanzati when he visited Rome that year.

[18] Historian Bogdan Krizman claims that the change came about because Pavelić involved Kvaternik in planning the assassination of King Alexander I of Yugoslavia in Marseille that year, which Frank resented.