In 1919, on behalf of Catholic bishops of the Kingdom of Serbs, Croats and Slovenes, he drafted a memorandum seeking recognition of the new state by the Holy See and personally handed it to Pope Benedict XV.

[4] After the proclamation of the 6 January Dictatorship in 1929, Rittig agreed with Mile Budak and Ante Pavelić to work to undermine Yugoslavia, but ultimately decided to promote a policy of Croatian-Serbian reconciliation through a compromise with King Alexandar.

[5] At a session of the Zagreb Assembly held on November 28, 1929, Rittig delivered a speech in which he strongly criticized Pavelić, who, according to him, worked in the service of Italian and Hungarian interests.

[6] Following the assassination of King Alexander in 1934, Rittig, alongside forty other dignitaries, signed a memorandum for the regulation of the interior affairs in the Kingdom of Yugoslavia, addressed to regent Prince Paul with the first request being the release of Vladko Maček from prison.

[7] In 1939, Rittig gave refuge to the persecuted Poles, Czechs and Jews and actively participated in the work of the Committee for War Refugees founded by Archbishop Aloysius Stepinac.

On 30 June 1941, he fled Zagreb after the establishment of the so-called Independent State of Croatia (NDH), when he found out he was to be arrested as the enemy of the regime.

[11] Between 1944 and 1954, Rittig served as a chairman of the Religious Affairs Commission of the People's Republic of Croatia which was founded by his efforts on 25 August 1944 at the ZAVNOH's third session.

[4] Rittig unsuccessfully urged the Yugoslav federal government to regulate its relations with the Catholic Church for the sake of peace and interethnic unity.

[13] Rittig pointed out that the vast majority of the Catholic bishops accepted the new government, but that they were confused and distrustful because it unlawfully interfered with religious freedom.