The early modern period in the lands of the Croatian-Slavonic Kingdom was a time of governmental change and constant Ottoman danger. It introduced new rulers from the house of Habsburg in 1526 and placed the Hungarian-Croatian Kingdom within the even larger political institution of the Holy Roman Empire from which religious conflicts began to spread, affecting the political situation. The Croatian-Slavonian magnates and other nobility were faced with the need to create new strategies in order to maintain their influence and political power, especially as the political center of the Kingdom shifted from the Hungarian area to Vienna. In the wider European area, the authority which the Catholic Church maintained throughout the Middle Ages was put into question due to religious reform and formation of confessional churches. As Catholic rulers, the Habsburgs carried out a counter-reformation policy which varied in intensity depending on the political and institutional peculiarities of the states. Religious conflicts soon became a first-class political issue, and religious policies created a space of resistance which was also used by the nobles in Croatia and Slavonia in the 16th and 17th centuries. Some of the local magnate families managed to maintain the Protestant confession despite the opposition of the Parliament, which, in cooperation with the ruler and the Zagreb diocese, developed an explicit Catholic-oriented religious policy. The middle and lower nobility found their political partners in the Church and the Habsburg rulers. One of the theories that explains the connection between the church and the government during the creation of a disciplined society and the construction of the state is the theory of confessionalization. This model is applicable for the Croatian-Slavonian Kingdom, where during a large part of the 16th century political tensions were visible between some of the Protestant magnates and the middle and lower nobility.