In 1817 King Friedrich Wilhelm III of Prussia called for a union of the Lutheran and Reformed churches. In February 1822 he ordered a common liturgy. The Old Lutherans rejected both. Pastors were suspended, and in 1834 the minister Altenstein asked for military help. In 1837 and 1838 nearly 2,000 Old Lutherans emigrated. Only in 1845 did the next king allow them their own congregations.
On 16 March 1973 Lutheran, Reformed and United churches agreed on the Leuenberg Concord. They granted each other fellowship at the pulpit and at the Lord’s Supper. Die Konkordie lässt die verpflichtende Geltung der Bekenntnisse in den beteiligten Kirchen bestehen. The concord leaves the binding force of each church’s confession in place.