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. In the 1920s, the Second Polish Republic and Lithuania, and in the 1950s to 1970s, East Germany, the People's Republic of Poland, and the Soviet Union, imposed permanent or temporary organizational divisions, eliminated entire congregations, and expropriated church property, transferring it either to secular uses or to different churches more favoured by these various governments. In the course of the Second World War, church property was either damaged or destroyed by strategic bombing, and by war's end, many parishioners had fled from the advancing Soviet forces. After the war, complete ecclesiastical provinces vanished following the flight and expulsion of Germans living east of the Oder-Neiße line. The two post-war periods saw major reforms within the Church, strengthening the parishioners' democratic participation. The Church counted many renowned theologians as its members, including Friedrich Schleiermacher, Julius Wellhausen (temporarily), Adolf von Harnack, Karl Barth (temporarily), Dietrich Bonhoeffer, and Martin Niemöller (temporarily), to name only a few. In the early 1950s, the church body was transformed into an umbrella, after its prior ecclesiastical provinces had assumed independence in the late 1940s. Following the decline in number of parishioners due to the German demographic crisis and growing irreligion, the Church was subsumed into the Union of Evangelical Churches in 2003. Status and official names The many changes in the Church throughout its history are reflected in its several name changes. These include: 1817–1821: The church union was still being regulated by Prussian officials, and no official name was taken up for it yet. Informal names reported elsewhere included Prussian Union of Churches and the Union of Churches in Prussia. 1821–1845: Evangelical Church in the