After the Frankish conquests in the Early Middle Ages (7th to 10th century) took them to the edges of today's Palatinate Forest, there was increasing population pressure in the Middle Ages (10th to 13th century), especially through the initiatives of the nobility and the church, e.g. through the establishment of monasteries such as the Cistercian abbeys of Otterberg (1144) and Eußerthal (1148), the colonization and development of the mountains. Areas that could be used for agriculture were cleared and settled permanently. This development reached its peak in the region during the era of the Salian (10th-12th centuries) and Hohenstaufen (12th and 13th century) emperors, with the construction of Trifels Castle and other castles in the surrounding area that, for a time, made it the centre of power of the empire.