German missionaries such as Vicelinus converted the Obotrites to Christianity. In 1170 they acknowledged the suzerainty of the Holy Roman Empire, leading to Germanisation and assimilation over the following centuries. The ruling clan of the Obotrites kept its power throughout the Germanisation and ruled their country (except of a short interruption in Thirty Years' War) as House of Mecklenburg until the end of monarchies in Germany in November Revolution 1918.