The situation on the eastern frontier from 260 CE onwards was mainly catalyzed by the crisis of the third century, during which the Roman Empire suffered unprecedented in-fighting for control of the throne, and the death of Emperor Valerian in Persian captivity. In 267 CE, the death of Odaenathus, loyal ruler of the Palmyrene Kingdom, led to the establishment of the Palmyrene Empire. Queen Zenobia began a short-lived campaign against Rome between 270–272 CE, during which she declared herself Empress, until she was defeated and Palmyra was destroyed in 273 CE. Under Emperor Diocletian’s reign, between 284¬–305 CE, Rome began a new era of structural reform and enjoyed much increased stability. He began a campaign in 298 CE against Persian King Narseh who had launched attacks against Armenia. Once Narseh had been defeated and a peace deal agreed, Rome gained control of a large portion of Armenia.
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