Trebonianus Gallus in the context of "Gothic War (248–253)"

Early Christians were heavily persecuted throughout the Roman Empire until the 3rd century. Although Christianity initially emerged as a small Jewish movement in 1st-century Judaea, it quickly branched off as a separate religion and began spreading across the various Roman territories at a pace that put it at odds with the well-established Roman imperial cult, to which it stood in opposition; Christians were vocal in their expressions of abhorrence towards the beliefs and practices of Roman paganism, such as deifying and making ritual sacrifices to the Roman emperor or partaking in other methods of idolatry. Consequently, the Roman state and other members of civic society routinely punished Christians for treason, various rumoured crimes, illegal assembly, and for introducing an alien cult that drove many Roman people to apostasy in favour of Jesus Christ. According to Tacitus, the first wave of organized persecution occurred under Nero (r. 54–68), who blamed Christians for the Great Fire of Rome in 64. A number of mostly localized persecutions occurred during the reign of Marcus Aurelius (r. 161–180). After a lull, persecution resumed under Decius (r. 249–251) and Trebonianus Gallus (r. 251–253). The Decian persecution was particularly extensive, as Decius strived to restore the Roman golden age in part by forcing pagan practices upon the Christian community. Another wave of persecution began under Valerian (r. 253–260), but ceased abruptly after he was captured and taken prisoner by the Sasanian Empire during the Battle of Edessa of the Roman–Persian Wars. Under his successor Gallienus (r. 253–268), whose reign was marred by rapidly escalating military conflicts of the Crisis of the Third Century, the first ever decree of tolerance was issued for Christian practices and places of worship, although it stopped short of recognizing Christianity as a religion with legal status.

Emperor Diocletian (r. 283–305) began the Diocletianic persecution, which was the final and the most severe wave of persecution of Christians by the Roman state. It was enforced until the accession of Galerius (r. 305–311), who issued the Edict of Serdica, and the death of Maximinus Daza (r. 310–313). After Constantine the Great (r. 306–337) defeated his rival Maxentius (r. 306–312) at the Battle of the Milvian Bridge in October 312, he and his co-emperor Licinius issued the Edict of Milan, which decriminalized Christianity and suppressed pagan populations throughout the Roman Empire. In 380, Theodosius I (r. 379–395) issued the Edict of Thessalonica, officially establishing Christianity as the Roman state religion. It was also during the reign of Theodosius I that pagan practices were overtly deemed punishable offenses, which laid the framework for early Byzantine anti-pagan policies.

Quintus Herennius Etruscus Messius Decius (died c. June 251), known simply as Herennius Etruscus, was briefly Roman emperor in 251, ruling jointly under his father Decius. His father was proclaimed emperor by his troops in September 249 while in Pannonia and Moesia, in opposition to Philip. Decius defeated Philip in battle, and was then proclaimed emperor by the Senate. Etruscus, still a child, was elevated to Caesar (heir) in 250, then further raised to Augustus (emperor) in May 251. When the Goths, under Cniva, invaded the Danubian provinces, he was sent with a vanguard, followed by the main body of Roman troops, led by Decius. They ambushed Cniva at the Battle of Nicopolis ad Istrum in 250, routing him, before being ambushed and routed themselves at the Battle of Beroe. Etruscus was killed in the Battle of Abritus the following year, alongside his father. After the deaths of both emperors, Trebonianus Gallus, who had been governor of Moesia, was elected emperor by the remaining Roman forces.

Marcus Aemilius Aemilianus (c. 207 – September 253), also known as Aemilian, was Roman emperor for two months in 253.

Commander of the Moesian troops, he obtained an important victory against the invading Goths and was, for this reason, acclaimed emperor by his army. He then moved quickly to Roman Italy, where he defeated Emperor Trebonianus Gallus at the Battle of Interamna Nahars in August 253, only to be killed by his own men a month later when another general, Valerian, proclaimed himself emperor and moved against Aemilian with a larger army.

Gaius Vibius Volusianus (Latin: Gaius Vibius Afinius Gallus Veldumnianus Volusianus; died August 253), commonly called Volusian, was a Roman emperor from 251 to 253, ruling with his father Trebonianus Gallus.

After Emperor Decius and his son and co-ruler Herennius Etruscus died in battle in June 251, Trebonianus Gallus was elected emperor in the field by the legion. Gallus raised Hostilian, the younger son of Decius, to augustus (co-emperor) and elevated Volusianus to caesar. After the death of Hostilian in July or August 251, Volusianus was raised to augustus. The short reign of Gallus and Volusianus was notable for the outbreak of a plague, which is said by some to be the reason for Hostilian's death, and for hostilities with the Sasanian Empire and the Goths. Volusianus and his father were killed in August 253 by their own soldiers, who were terrified of the forces of the usurper Aemilian which were marching towards Rome.

Cniva (fl. mid-3rd century AD) was a Gothic king who invaded the Roman Empire in the middle of the 3rd century AD. His regnal years are uncertain. He successfully captured the city of Philippopolis (Plovdiv in Bulgaria) in 250 and killed Emperor Decius and his son Herennius Etruscus at the Battle of Abritus as he was attempting to leave the Empire in 251. This was the first time a Roman Emperor had been killed in combat against foreigners. He was allowed by the new Emperor Trebonianus Gallus to leave with his spoils and was paid tribute to stay out of the empire.