Middle Ages, Slavic tribal confederacies, and then Slavic states, dominated. Silesia was part of Great Moravia, then Kingdom of Bohemia and finally the Piast monarchy of Poland. The tribal differences started to disappear after the consolidation of Poland in the 10th and 11th centuries. The main factors of this process were the establishment of a single monarchy that ruled over all Polish tribes, as well as creation of a separate ecclesiastical organization within the boundaries of the newly established Polish state. The names of the smaller tribes disappeared from historical records, as well as the names of some prominent tribes. However, in some places, the names of the most important tribes transformed into names representing the whole region, such as Mazovians for Mazovia, and Silesians for Silesia. As a result of the fragmentation of Poland, some of those regions were again divided into smaller entities, such as the division of Silesia into Lower Silesia and Upper Silesia). However, the tribal era was already over, and these divisions reflected only political subdivisions of the Polish realm. Within Poland, from 1177 onward, Silesia was divided into many smaller duchies. In 1178, parts of the Duchy of Kraków around Bytom, Oświęcim, Chrzanów and Siewierz were transferred to the Silesian Piasts, although their population was of Vistulan and not of Silesian descent. Parts of those territories were bought by the Polish kings in the second half of the 15th century, but the Bytom area remained in the possession of the Silesian Piasts, even though it remained a part of the Diocese of Kraków. Between 1327 and 1348, the duchies of Silesia came under the suzerainty of the Crown of Bohemia, which was then passed to the Habsburg monarchy of Austria in 1526. Beginning in the 13th century, Slavic Silesia began to be settled by Germans from various parts of Germany, including Prussia and Austria. This led to changes in the ethnic structure of the province. In the Middle Ages, various German dialects of the new settlers became widely used throughout Lower Silesia and some Upper Silesian cities. However, after the era of German colonization, the Polish language was still predominant in Upper Silesia and parts of Lower and Middle Silesia north of the Odra river. Germans usually dominated large cities, and Poles mostly lived in rural areas. This required the Prussian authorities to issue official documents in Polish, or in German and Polish. The