As in France, so in Germany: the impetus for encastellation was provided, not by a strong monarch, but by the weakening of royal authority.
In Prussia, during the Drang nach Osten and the Northern Crusades of the twelfth and thirteenth centuries, encastellation was the result of the Margraves of Brandenburg and the Teutonic Knights, who, among others, conquered the land from the pagan Prussians.