Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
C. Messius Quintus Trajanus a Roman emperor, was born at Bubalia, in Lower Pannonia, towards the close of the second century. Being sent in 249 by the emperor Philippus to restore to subordination the army of Moesia, which was in a state of revolt, the troops proclaimed him emperor against his will, and forced him to march upon Italy. Philippus having been defeated and slain, Decius assumed the government of the empire in the end of the year A.D. 249, but his brief reign was one of restless warring with the Goths, fighting against whom he was killed near Abricium, in the close of the year 251. Decius was an emperor of more than ordinary ability, but his reign was stained by a bloody persecution of the Christians. In point of time this persecution ranks as the seventh, but in point of cruelty it was only equaled by that of Diocletian. (See Persecutions).
For about forty years prior to the accession of Decius the Christians had enjoyed peace, which only in some parts of the Roman empire was, for a short time, interrupted by a. decree of the emperor Maximin. The effect of this peace upon the religious life of the Church was, in general, not favorable. Cyprian, Origen, and other ecclesiastical writers complain that worldliness, avarice, and other vices had become prevalent, and that marriages of Christians with pagans had become frequent. Soon after his accession to the throne (probably at the beginning of the year 250), Decius issued a severe decree against the Christians. The decree itself is lost, the Edictum Decii Augusti contra Christianos, which was published in 1664 at Toulouse by Bernard Medonius from Acts of the Martyrs, being spurious, as has been shown by Tillemont and Mosheim. The contents of the decree are, however, fully noticed by Gregory of Nyssa and other ancient writers. It ordered the civil magistrates to destroy Christianity by threatening Christians with the severest punishments and by using against them tortures of every kind. It was sent to the governors of all the provinces, and most of them hastened to execute it. They promulgated the decree, and demanded that within a certain time every Christian should appear before the civil magistrate, and publicly declare his renunciation of the Christian faith; in the case of refusal, he was to suffer severe punishment, even death. Dionysius of Alexandria and Cyprian have given detailed description, of the persecution in the region of Carthage and Alexandria. Cyprian says that at the first news of the impending persecution a majority of the brethren hastened to renounce the faith, but his account is suspected of exaggeration. That the number of apostates was very large is also reported by Eusebius. Of those who remained faithful, most left the cities and sought refuge in solitude, Among this class were many of the most celebrated bishops, as Cyprian, Dionysius of Alexandria, and Gregory Thaumaturgus. This action was generally approved by the Church. The number of those, however, who neither fled nor apostatized was so great that, as ‘ soon as the time appointed for the execution of the decree arrived, the prisons were not sufficient to contain those who were arrested. Decius wished executions to be avoided, but every conceivable torture, if necessary, to be resorted to. Most of the civil magistrates vied with each other in inventing the most cruel tortures; only a few showed a spirit of sympathy and leniency. The number of those who succumbed to the torture (lapsi) was very large. Many procured false certificates that they had abjured the faith (libellatici). On the other hand, however, the number of those who died or were mutilated for the faith was considerable. In Rome, Antioch, and Jerusalem the several bishops were massacred; Origen, famous among the early fathers, was subjected to the most acute tortures. All the ancient martyrologies abound in names of those who are reported to have suffered martyrdom under Decius, and Tillemont spent much time and labor to sift the genuine reports from the spurious (Memoires, 3, 133- 189). Fortunately, the persecution of Decius did not last long. About Easter, 251, Cyprian could return from his concealment. The war which the emperor had to carry on against the Goths, his absence from Rome, the inroads of barbarians into the African provinces, and several insurrections, greatly moderated the persecution at the beginning of the year 251. When Decius, towards the close of the year, fell in a battle against the Goths, the Christians were set at liberty. — Herzog, Real-Encyklop. 3, 309; Wetzer und Welte, Kirchen.-Lex. 3, 59; Neander, Church History (Torrey's transl.), vol. 2.
The Nuttall Encyclopedia 
Roman emperor from 249 to 251; was a cruel persecutor of the Christians; perished in a morass fighting with the Goths, who were a constant thorn in his side all through his reign.