While campaigning, the Praetorians were the equal of any formation in the Roman Army. Seldom used in the early reigns, they were quite active by AD 69. Under Domitian and Trajan, the guard took part in wars from Dacia to Mesopotamia, while with Marcus Aurelius, years were spent on the Danube frontier. Throughout the 3rd century, the Praetorians assisted the emperors in various campaigns.