(Caius Messius Quintus Decius) (dē'shəs), 201–51, Roman emperor (249–51), b. Pannonia. He was sent by Philip (Philip the Arabian) to quell a mutiny, but when the soldiers hailed him as emperor, he marched at their head, defeated and killed Philip near Verona, and accepted the title of emperor, adding Trajan (Traianus) to his name. He undertook to rebuild the state, and in an effort to revive the state religion he persecuted the Christians vigorously. He was killed in the attempt to repel an invasion of the Goths into Moesia and was succeeded by Gallus.