Philip's rise to prominence began through the intervention of his brother Priscus, who was an important official under the emperor Gordian III. His big break came in 243, during Gordian III's campaign against Shapur I of Persia, when the Praetorian prefect Timesitheus died under unclear circumstances. At the suggestion of his brother Priscus, Philip became the new Praetorian prefect, with the intention that the two brothers would control the young Emperor and rule the Roman world as unofficial regents. Following a military defeat, Gordian III died in February 244 under circumstances that are still debated. While some claim that Philip conspired in his murder, other accounts (including one coming from the Persian point of view) state that Gordian died in battle. Whatever the case, Philip assumed the purple robe following Gordian's death. According to Edward Gibbon:  His rise from so obscure a station to the first dignities of the empire seems to prove that he was a bold and able leader. But his boldness prompted him to aspire to the throne, and his abilities were employed to supplant, not to serve, his indulgent master. Philip was not willing to repeat the mistakes of previous claimants, and was aware that he had to return to Rome in order to secure his position with the senate. However, his first priority was to conclude a peace treaty with Shapur I of Persia, and withdraw the army from a potentially disastrous situation. Although Philip was accused of abandoning territory, the actual terms of the peace were not as humiliating as they could have been. Philip apparently retained Timesitheus’ reconquest of Osroene and Mesopotamia, but he had to agree that Armenia lay within Persia's sphere of influence. He also had to pay an enormous indemnity to the Persians of 500,000 gold denarii. Philip immediately issued coins proclaiming that he had made peace with the Persians ("pax fundata cum Persis"). Leading his army back up the Euphrates, south of Circesium Philip erected a cenotaph in honor of Gordian III, but his ashes were sent ahead to Rome, where he arranged for Gordian III's deification. Whilst in Antioch, he left his brother Priscus as extraordinary ruler of the Eastern provinces, with the title of "rector Orientis". Moving westward, he gave his brother-in-law Severianus control of the provinces of Moesia and Macedonia. He eventually arrived in Rome in the late summer of 244, where he was confirmed "Augustus".