The "Ostsiedlung" (lit. Eastern settlement) is the term for a process of largely uncoordinated immigration and chartering of settlement structures by ethnic Germans into territories, already inhabited by Slavs and Balts east of the Saale and Elbe rivers, such as modern Poland and Silesia and to the south into Bohemia, modern Hungary and Romania during the High Middle Ages from the 11th to the 14th century. The primary purpose of the early imperial military campaigns into the lands to the east during the 10th and 11th century, was to punish and subjugate the local heathen tribes. Conquered territories were mostly lost after the troops had retreated, but eventually were incorporated into the empire as marches, fortified borderlands with garrisoned troops in strongholds and castles, who were to ensure military control and enforce the exaction of tributes. Contemporary sources do not support the idea of policies or plans for the organized settlement of civilians.