Thirty Years' War
Following the 30 Years' War time, much loss of life of soldiers caused there to be many single woman and girls. The population was reduced from 17 million to only 4 million. As a result, there were areas in Germany where men were allowed to have 2 wives. More on this topic can be found in an article by Udo Macholdt in the Brandenburgische Genealogische publication "Roter Adler". Year 4, Bd. II, Heft 1 1/2009.