Counter-Reformation in the Polish–Lithuanian Commonwealth

Counter-reformation in Poland refers to the response (Counter-Reformation) of Catholic Church in Poland (more precisely, the Kingdom of Poland until 1568, and thereafter the Polish-Lithuanian Commonwealth) to the spread of Protestantism in Poland (the Protestant Reformation). Counter-reformation in Poland lasted from the mid-16th century until the mid-18th century and ended with the victory of the Catholic Church, which succeeded in significantly reducing the influence of Protestantism in Poland.

Poland emerged as one of the main terrains of struggle between the Protestant Reformation movement and the Catholic Church's counter-reformation.Lutheranism was popular among German-descent townsfolk, and Calvinism among the nobility. A year after Luther made his theses public, they were preached in Danzig (Gdańsk), and soon spread over West Prussia province of Poland. From there Protestantism spread to East Prussia, Greater Poland, Lesser Poland and other Polish provinces, as well as Grand Duchy of Lithuania. In 1573 the Protestants, commanding a majority in the Sejm (parliament), scored a major political victory by passing a law of religious tolerance, the Warsaw Confederation. Towards the end of the 16th century, it can be estimated (through the number of parishes) that about a seventh of the Christian population in the Polish-Lithuanian Commonwealth were Protestant. In the 16th century, Poland was a haven for many refugees fleeing persecution from less tolerant parts of Europe, harboring not only Catholics and Protestants, but also people of Orthodox, Judaic and even Muslim faiths.

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