EUROPEAN HERITAGE LIBRARY WWW.EUROHERITAGE.NET From the 13th century onward, as the Polish Kingdom declined, the German Empire charted crusading orders like the Teutonic Order as vassals to Christianize Europe. Invited by Hungarian and Polish authorities to pacify and Christianize Prussia, the Germans instead conquered a theocratic state stretching from Pommern to Estonia as a vassal of the German Empire. By the 15th century, as Poland gradually merged with Lithuania and became strong, Slavs under the Teutonic Order's authority requested aid from Poland-Lithuania to expel the Germans. Thus began the 13 Years' War and the Great War (Poland-Lithuania-Teutonic Order War). By the end of the wars, the Teutonic Order had been crushed (but still survived), and Poland-Lithuania gradually became one of Europe's great empires. The Germans would return to conquer most of the region from the 17th century until after World War II. EUROPEAN HERITAGE LIBRARY WWW.EUROHERITAGE.NET