The 4th century was characterised by strong emperors fighting in the frontiers when not fending off usurpers, many of whom started in Britain, including Constantine the Great. This provides a background to the 4th century feast activity that follows.
The Tetrarchy (four emperors co-ruling) began to unravel in the northern frontier of Britain with the death of Constantius Chlorus in York in 306. Rather than power passing on to his officially nominated junior emperor, Constantius’ son, Constantine was proclaimed Emperor by the soldiers in York.
Constantine acted quickly, and through the course of a successful civil war became the sole emperor in 324. Constantine is particularly noted as a Christian emperor (see Step 4.18). Yet he did not convert the Roman Empire to Christianity in any official capacity. It is clear that Christianity was used by Constantine politically as a way of providing the Empire with a single, unifying religion.
Constantine recognised the importance of defended frontiers and sought to expand the field armies (the comitatenses) without reducing the numbers of frontier soldiers (the limitanei
), described in 2.14.
When Constantine died in 336, he was succeeded by his three surviving sons, Constantine II, Constantius II, and Constans. The brothers were successful in killing nearly all other male relatives, and therefore removing possible political rivals. They then split the Empire into three praefectures, each bearing one of the sons of Constantine as its ruler.
The brothers soon quarrelled, and jealousy led to civil war. Constantine II, who ruled over Britain, Gaul, and Spain, demanded lands in North Africa from his younger brother Constans. Constantine II died in battle in 340 at the hands of Constans’ troops. Constans and Constantius II then split the Empire between themselves into a Western half under Constans and an Eastern half under Constantius II.
Further civil war in 350, led by a general named Magnentius, resulted in Constantius II as the sole emperor of the Empire. He was joined by Julian, his cousin, as the junior emperor in 355. Julian proved to be an effective junior-emperor, and in 360 his soldiers elevated him as the equal of Constantius II. The two prepared to fight a civil war, but this was avoided when Constantius fell ill and died in 360. Julian became the sole emperor, and in 363 he embarked on a campaign against the Persians where he died.
Jovian was quickly appointed as the emperor by a ruling council, and he negotiated a hasty treaty with the Persians to end the war. During the return to Constantinople, Jovian died.
In 364, Valentinian was chosen to wear the purple, and he appointed his brother Valens as co-emperor. Valentinian ruled the Western Empire for 11 years, dying in 375 of a fit. It was during the reign of Valentinian in 367 that Britain reportedly suffered from a barbarian conspiracy.
Valentinian was succeeded by his son, Gratian, in the West, and his brother Valens continued to rule in the East. However, in 378 Valens died at the disastrous Battle of Adrianople. Theodosius was named as the Emperor for the East, since Valens had no heirs.
In 383, Gratian was killed by another usurper who started in Britain, Magnus Maximus, who was eventually defeated in 387 by Theodosius. The victory left Theodosius in charge of the entire Empire, and when he died in 395, it was his sons that were the emperors: Arcadius in the East and Honorius in the West.
Honorius was the last emperor to govern Britain, and it was during his reign, around 410, that Britain ceased to be a Roman dominion, following the death of another British usurper, Constantine III.
The 4th century can be described as one of constant warfare, both civil and foreign. Usually, emperors were engaged in warfare in the frontiers, normally against the Persians in the East, or fighting various groups such as Goths, Alamans, and Franks across the Danube and Rhine rivers. Usurpers and civil wars, however, were relatively frequent and always became a priority for the emperors.
This nearly constant state of warfare had two consequences that directly impacted the frontiers:
- the soldiers generally accrued experience rapidly
- there was always a need for more soldiers!