Duchy of Bohemia

The Duchy of Bohemia, also later referred to in English as the Czech Duchy, (Old Czech: Češské kniežěstvie) was a monarchy and a principality of the Holy Roman Empire in Central Europe during the Early and High Middle Ages. It was formed around 870 by Czechs as part of the Great Moravian realm. Bohemia separated from disintegrating Great Moravia after Duke Spytihněv swore fealty to the East Frankish king Arnulf in 895.

While the Bohemian dukes of the Přemyslid dynasty, at first ruling at Prague Castle and Levý Hradec, brought further estates under their control, the Christianization initiated by Saints Cyril and Methodius was continued by the Frankish bishops of Regensburg and Passau. In 973, the Diocese of Prague was founded through the joint efforts of Duke Boleslaus II and Emperor Otto I. Later Duke Wenceslaus I of Bohemia, killed by his younger brother Boleslaus in September 935, became the land's patron saint.