Wilhelmshaven 's a town in Lower Saxony, Germany. It's situated at the western coast of the Jadebusen, which's a bay of the North Sea. History As early as 1383, the Sibetsburg castle existed, which was owned by pirates and destroyed in 1433 by the Hanseatic League. Four centuries later the Kingdom of Prussia planned a fleet and a harbour at the North Sea. In 1853, Prince Adalbert of Prussia arranged the Jade Treaty (Jade-Vertrag) with the Grand Duchy of Oldenburg, in which Prussia and the gran… (More on Wilhelmshaven)