In 1226, Konrad I, Duke of Masovia in north-eastern Poland, appealed to the Knights to defend his borders and subdue the pagan Baltic Old Prussians, allowing the Teutonic Knights use of Chełmno Land as a base for their campaign. This being a time of widespread crusading fervor throughout Western Europe, Hermann von Salza considered Prussia a good training ground for his knights for the wars against the Muslims in Outremer. With the Golden Bull of Rimini, Emperor Frederick II bestowed on the Order a special imperial privilege for the conquest and possession of Prussia, including Chełmno Land, with nominal papal sovereignty. In 1235 the Teutonic Knights assimilated the smaller Order of Dobrzyń, which had been established earlier by Christian, the first Bishop of Prussia.