In 1817, Frederick William III of Prussia ordered the Lutheran and Reformed churches in his territory to unite, forming the Evangelical Church of the Prussian Union. The unification of the two branches of German Protestantism sparked the Schism of the Old Lutherans. Many Lutherans, called "Old Lutherans", despite imprisonment and military force, chose to leave the established churches and form independent church bodies, or "free churches" while others left for the United States and Australia. A similar legislated merger in Silesia prompted thousands to join the Old Lutheran movement. The dispute over ecumenism overshadowed other controversies within German Lutheranism.