The Conquest of Dacia was completed by Emperor Trajan from the years 851-870 (98-117 AD). Prior to this Dacians were united in one Kingdom. Dacia was subject to some of the most energetic colonization and mining operations in the Empire. Dacia came under frequent attack prior to the major conquests of Emperor Marcus Aurelius, however, these subsided once there were hardly any enemies which were not part of the Roman Hegemony.