The third workshop of the research group Negotiating Sovereignty at the HUN-REN Institute of History took place on November 10, 2023. The project, led by András Fejérdy and funded by the European Research Council (ERC), has been running for a year. The research examines the changing state-church relations in the Habsburg Empire and its successor states through the institution of the Catholic bishops’ and archbishops’ oaths of allegiance to the monarch (or to the state). During the one-day workshop, one group of participants presented their findings on the ‘long 19th century’. Katalin Pataki explored the background to the oath of allegiance introduced during the reign of Joseph II, with particular reference to the oath of allegiance to the Pope and the prohibition of alienation of church property. Tomasz Hen-Konarski looked at the organisation of the Catholic Church in the Russian Empire between 1763 and 1918 and its state regulation, suggesting directions for further research. Miklós Tömöry reviewed the oaths of the Catholic bishops and archbishops of Croatia-Slavonia between 1849 and 1915, outlining negotiations of episcopal appointments in the period of Croatian-Hungarian ’sub-dualism’. Senior Research Fellow Emília Hrabovec’s lecture focused on the period of state socialism, one of the main foci of the project. She examined the ecclesiastical policies of the communist transition of the Czechoslovak Republic, the appointment of bishops in Slovakia in the light of the Holy See’s documents and the Vatican’s policies towards the Stalinist state.