Philip the Arab became emperor under mysterious circumstances, and might have killed former emperor Gordian III. He was of low-birth Arabian origin from the Roman province of Syria and had to travel to Rome immediately to secure his throne. In 244 he made an unfavourbable peace with king Shapur I of Persia, by giving away suzerainty of Armenia. Osroene became a vassal state again. The senate accepted his emperorship.
In 245, Philip refused to pay tribute to the Carpi. The Carpi retaliated by laying waste to Moesia Inferior. Philip defeated the Carpi and invaded the carpi homeland, making peace with them in 247. Germanic peoples invaded Pannonia and were repulsed as well.
In 248, Pacatianus revolted in Moesia, Jotapianus in Syria, and there were perhaps also revolts in Germania Superior under Silbannacus and in Dacia under Sponsianus. Anger about the peace treaty with Persia was one of the reasons for the revolts. The Germanic Peoples and Carpi used this opportunity to invade Moesia and Pannonia again. Philip named Decius as the new commander of the Danube armies, who defeated Pacatianus.
In 249, the Danube armies revolted again, naming Decius as emperor. Decius marched to Italy and defeated and killed Philip at the Battle of Verona. In the meanwhile, Germanic and Carpian invasions continued. Marcianopolis was sacked by the Goths.