German Bohemians, later known as the Sudeten Germans, were ethnic Germans living in the lands of the Bohemian Crown, which later became an integral part of the state of Czechoslovakia. Before 1945, Czechoslovakia was inhabited by over three million such German Bohemians,[4] comprising about 23 percent of the population of the whole republic and about 29.5 percent of the population of Bohemia and Moravia.[5] Ethnic Germans migrated into the Kingdom of Bohemia, an electoral territory of the Holy Roman Empire, from the 11th century, mostly in the border regions of what would later be called the "Sudetenland", named after the Sudeten Mountains.[6] This process of German expansion was known as Ostsiedlung ('Settling of the East').