Catholic activities in Early modern Europe
During the 16th century, under the influence of the Catholic Counter-Reformation, rising pressures towards Orthodox Christians in White Ruthenia and other Eastern parts of Polish-Lithuanian Commonwealth led to the enforcement of the Union of Brest in 1595-96. Until that time, most Belarusians and Ukrainians who lived under the rule of Polish-Lithuanian Commonwealth were Orthodox Christians. Pressed by the state authorities, their hierarchs gathered in synod in the city of Brest and composed 33 articles of Union, which were accepted by the Roman Catholic Church.
At first, the Union appeared to be successful, but soon it lost much of its initial support, mainly due to its forceful implementation on the Orthodox parishes and subsequent persecution of all who did not want to accept the Union. Enforcement of the Union stirred several massive uprisings, particularly the Khmelnytskyi Uprising, of the Zaporozhian Cossacks and together alliance of Ukrainian Catholics and Belarussian-Ukrainian Orthodox because of which the Commonwealth lost Left-bank Ukraine.
In 1656, Greek Orthodox Patriarch of Antioch Macarios III Zaim lamented over the atrocities committed by the Polish Catholics against followers of Eastern Orthodoxy in various parts of Ukraine. Macarios was quoted as stating that seventeen or eighteen thousand followers of Eastern Orthodoxy were killed under hands of the Catholics, and that he desired Ottoman sovereignty over Catholic subjugation, stating:
God perpetuate the empire of the Turks for ever and ever! For they take their impost, and enter no account of religion, be their subjects Christians or Nazarenes, Jews or Samaritians; whereas these accursed Poles were not content with taxes and tithes from the brethren of Christ...
Since the many migrations of Serbs (predominantly and traditionally Eastern Orthodox) into the Habsburg Monarchy beginning in the 16th century, there were efforts to Catholicize the community. The Orthodox Eparchy of Marča became the Catholic Eparchy of Križevci after waves of Uniatization in the 17th and 18th centuries. Notable individuals active in the Catholicisation of Serbs in the 17th century include Martin Dobrović, Benedikt Vinković, Petar Petretić, Rafael Levaković, Ivan Paskvali and Juraj Parčić. Catholic bishops Vinković and Petretić wrote numerous inaccurate texts meant to incite hatred against Serbs and Orthodox Christians, some of which included advice on how to Catholicize the Serbs.