Political map of Europe & the Mediterranean 26 April 142 (Principate of Antoninus Pius): Hadrian died in 138 and was succeeded by Antoninus Pius. Antoninus’ 22-year reign was the most peaceful of all the Roman emperors, with no known major revolts or wars. However, he did expand Roman power by extending the frontier in Britain to the Firth of Forth (Antonine Wall) and by appointing a new king of Armenia (Sohaemus of Armenia) (displacing Shah Vologases III of Parthia).