Czech tribes in present-day central Bohemia started to build a unified state under the influence of the neighboring Great Moravia in the 880s under Prince Borivoj from the Premyslid house, who was baptised by the Great Moravian bishop Methodius in 874. In the 880s he moved his seat to Prague and started to subjugate the Vltava Basin. The emerging Bohemian Principality (often incorrectly called a kingdom already for this time period) was conquered by Great Moravia 888/890. In 895, the Prince of Bohemia becomes a vassal of the East Frankish king Arnulf of Carinthia. The Bohemian Principality definitively emerged in 995 when the Premyslid chiefs--members of the tribe called Czechs (one of the tribes in Bohemia, from which the Czechs derive their name)--unified neighboring Czech tribes and established a form of centralized rule.
Cut off from Byzantium by the Hungarian presence, the Bohemian Principality existed in the shadow of the Holy Roman Empire. In 950 the powerful emperor Otto I, a Saxon, led an expedition to Bohemia demanding tribute; the Bohemian Principality thus became a fief of the Holy Roman Empire and its king one of the seven electors of the emperor. The German emperors continued the practice of using the Roman Catholic clergy to extend German influence into Czech territory. Significantly, the bishopric of Prague, founded in 973 during the reign of Boleslav II (967-99), was subordinated to the German archbishopric of Mainz. Thus, at the same time that Premyslid rulers utilized the German alliance to consolidate their rule against a perpetually rebellious regional nobility, they struggled to retain their autonomy in relation to the empire.
After a struggle with Poland and Hungary, the Bohemian Kingdom acquired Moravia in early 11th century (see Great Moravia). Moravia, however, continued to be a separate margravate, usually ruled by a younger son of the Bohemian king. Because of complex dynastic arrangements, Moravia's link with the Bohemian Kingdom between the eleventh and sixteenth centuries was occasionally severed; during such interludes Moravia was subordinated directly to the Holy Roman Empire. Although Moravia's fate was intertwined with Bohemia's, in general it did not participate in Bohemia's civil and religious struggles. The main course of Czech history evolved in Bohemia proper.