After finishing his studies at the Faculty of Humanities and Social Sciences, University of Zagreb, he taught the Croatian language and literature at the Franciscan gymnasium in Široki Brijeg.

Known as a nationalist, he supported the puppet Independent State of Croatia (NDH), established by Nazi Germany and Italy in 1941.

As an official at the Ministry of Justice and Religion, Glavaš was charged with setting up the procedures and regulations for mass conversion of the Serb Eastern Orthodox population to Catholicism, even though the Catholic Church's hierarchy opposed such a programme.

Glavaš was born in Drinovci near Grude in the region of Herzegovina, at the time part of Austria-Hungary, to father Petar and mother Mara née Marinović.

After finishing the sixth grade in 1927, Glavaš paused his education and entered a one-year novitiate at the Franciscan friary in Humac, Ljubuški on 29 June 1927.

Glavaš remained in Lille another year and asked to return to Herzegovina, which Provincial Mate Čuturić granted on 1 July 1934.

Thus, Glavaš lived in the friary of the Croatian Franciscan Province of Saints Cyril and Methodius in Kaptol, Zagreb.

[8] This move was highly unpopular with the Serb-dominated officer corps of the military and some segments of the public: a large part of the Serbian population, as well as liberals and Communists.

[9] Military officers (mainly Serbs) executed a coup d'état on 27 March 1941 and forced the Regent to resign, while King Peter II, though only 17, was declared of age.

[12] On 10 April 1941, the two Axis Powers, Germany and Italy, established its puppet Independent State of Croatia (NDH).

[14] Budak became Minister of Justice and Religion of the newly established NDH and asked the Herzegovinian Provincial Krešimir Pandžić on 10 May 1941 to allow Glavaš to become a member of his ministry.

[20] As an official of the Ministry of Justice and Religion, Glavaš was charged with setting up the procedures and regulations within the programme of the mass conversion of the Eastern Orthodox Serb population to Catholicism.

However, the government ignored the bishop's condemnation, announced the introduction of the new regulations in July 1941 and started recruiting individual priests to carry out the conversions.

In the summer and autumn of 1941, individual priests were sent out to rural areas to conduct the conversions, and Serbs agreed to convert, fearing for their lives.

The intimidating attitude of some priests, especially those in Herzegovina, together with the arbitrariness of conversions, led to the fact that they shook the legitimacy of the entire programme.

[24] Glavaš also managed to get the money earned from the assets of the Serbian Eastern Orthodox churches to the Franciscan friaries.

[25] Glavaš was involved in an affair of the episcopal appointment in Herzegovina when a secular priest Petar Čule was named the new bishop of Mostar-Duvno and the apostolic administrator of Trebinje-Mrkan.

[27] The Ustaše government complained that Čule's and the appointment of the Greek Catholic bishop Janko Šimrak occurred without consultation with them.

[28] At the time when Pavelić was preparing to celebrate his name day on the feast of Saint Anthony of Padua on 13 June 1942, he was informed by the Pope's delegate Giuseppe Masucci that if he would hold to this protest note, he would be automatically excommunicated per 2334 Code of Canon Law, and that this would obstruct the celebration of his name day.

[28] Few days after the protest note was issued,[29] Archbishop of Zagreb Aloysius Stepinac invited a high official in the Ministry of Justice and Religion together with Glavaš and threatened them both with excommunication if they don't refrain from their actions.

Glavaš refused to acknowledge the excommunication, claiming that he had no role in creating nor spreading the protest note against Čule's appointment.

[32] Before the entrance of the Partisans in Zagreb, the NDH government took the treasures of the Croatian National Bank, including gold, jewellery, and foreign currency, and put them in 42 boxes.

[34] In his testimony to OZNA from 10 June 1945, Glavaš said that he at first escaped to Austria, but after witnessing the chaotic situation of the escapees and malnourishment, he decided to return to Zagreb.