In 1230, following the Golden Bull of Rimini, Grand Master Hermann von Salza and Duke Konrad I of Masovia launched the Prussian Crusade, a joint invasion of Prussia intended to Christianize the Baltic Old Prussians. The Knights had quickly taken steps against their Polish hosts and with the Holy Roman Emperor's support, had changed the status of Chełmno Land (also Ziemia Chelminska or Kulmerland), where they were invited by the Polish prince, into their own property. Starting from there, the Order created the independent Monastic State of the Teutonic Knights, adding continuously the conquered Prussians' territory, and subsequently conquered Livonia. Over time, the kings of Poland denounced the Order for expropriating their lands, specifically Chełmno Land and later the Polish lands of Pomerelia (also Pomorze Gdańskie or Pomerania), Kujawy, and Dobrzyń Land.