In the final period of relations, Trajan reintroduced the Crassan phase of the Roman–Parthian historical cycle. In 114–116 CE, Trajan played the part of an opportunist bent on conquering Upper Mesopotamia, Babylonia, and Ctesiphon. In our view, Trajan failed, but he may have seen it differently. While decades of peace followed, future emperors emulated Trajan, resulting in fierce wars between Lucius Verus and Marcus Aurelius and Vologases IV in 166–161 CE, Septimius Severus and Vologases in 193–198 CE, and Caracalla and Macrinus and Artabanus IV in 214–217 CE. The rhetoric andreality of war were quite alive.