By: Mir M.Hosseini
After years of intrigue, Hadrianus was adopted and named successor just before Trajan's death. Three days after becoming the new Roman emperor, Hadrianus surrendered Trajan's conquests in Mesopotamia, considering them to be indefensible. He executed his senatorial opponents, abandoned Trajan's conquests in Armenia and Mesopotamia, and coped with unrest in Mauretania and Parthia. He traveled widely, and many of his accomplishments were related to his visits abroad. He began construction of Hadrian's Wall. His policy was peace through strength, even threat which also averted a war with Iran around 121.
Khosrau, the Parthian king had spent most of his life in wars with Trajan. Both nations entered a period of reconstruction and fortification after the peace treaty. Hadrianus succeeded in erecting massive walls in Britain, the Danube and Rhine of mostly wooden fortifications, forts, outposts and watchtowers thus improving communications and local area security.
Trajan, who had planned to extend the Roman frontier up to the river Tigris, marched southwards along the river Euphrates, capturing great parts of Babylonia up to the Persian Gulf and even Tisfun. He was campaigning in Asia when revolts broke out in conquered territories. On his retreat from there he attacked the Hatra in vain. Discouraged and ill, he died on his journey to Rome.