The Prussian Union of Churches (known under multiple other names) was a major Protestant church body which emerged in 1817 from a series of decrees by Frederick William III of Prussia that united both Lutheran and Reformed denominations in Prussia. Although not the first of its kind, the Prussian Union was the first to occur in a major German state.
It became the biggest independent religious organization in the German Empire and later Weimar Germany, with about 18 million parishioners. The church underwent two schisms (one permanent since the 1830s, one temporary 1934–1948), due to changes in governments and their policies. After being the favoured state church of Prussia in the 19th century, it suffered interference and oppression at several times in the 20th century, including the persecution of many parishioners.
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