A new period in hillfort development started during the 5th-8th centuries AD, when many new hillforts appeared, in most cases, along the main trades routes - rivers. During the 10th-11th centuries, some of the hillforts became military fortresses with strong fortifications (like hillforts in Tērvete, Talsi, Mežotne). Some of them are considered important political centres of the local peoples, who in this period were subjects of serious social political changes.