For the Military Orders the age of the Reformation was a period of severe crisis in which their very existence was challenged by protestant princes and reformers. Especially in the northern part of Europe the Hospitallers and the Teutonic Order faced serious losses. Religious convictions played an important role, but events were also influenced by processes of state building and the personal ambitions of the orders' leaders on all levels. These and other themes are treated in thirteen contributions by experts in the field, presenting the results of new research on the developments in diverse regions of Europe.