Early career Constantius's birthday was 31 March; the year is unknown, but his career and the age of his eldest son imply a date no later than c. 250. Constantius was a
Thracian or an
Illyrian. He was born in
Moesia Superior (later
Dacia Ripensis), a
Roman province on the south bank of the
Middle Danube. According to the unreliable
Historia Augusta he was the son of Eutropius, a
nobleman from the province of
Moesia Superior, and
Claudia, a niece of the emperors
Claudius Gothicus and
Quintillus. The same source also gives Claudius the nomina "
Flavius Valerius" to strengthen his connection to Constantius. Modern historians suspect this maternal connection to be a genealogical
fabrication created by his son
Constantine I, and that his family was of humble origins. '' on the reverse Constantius was a member of the
Protectores Augusti Nostri under the emperor
Aurelian and fought in the east against the secessionist
Palmyrene Empire. While the claim that he had been made a
dux under the emperor
Probus is probably a fabrication, he certainly attained the rank of
tribunus within the army, and during the reign of
Carus he was raised to the position of
praeses, or governor, of the province of
Dalmatia. It has been conjectured that he switched allegiances to support the claims of the future emperor
Diocletian just before Diocletian defeated
Carinus, the son of Carus, at the
Battle of the Margus in July 285. In 286, Diocletian elevated a military colleague,
Maximian, to the throne as co-emperor of the western provinces, while Diocletian took over the eastern provinces, beginning the process that would eventually see the division of the
Roman Empire into two halves, a
Western and an
Eastern portion. By 288, his period as governor now over, Constantius had been made
praetorian prefect in the west under Maximian. To consolidate the ties between himself and Emperor Maximian, Constantius married the emperor's daughter,
Theodora. At
Mediolanum (
Milan) on 1 March 293, Constantius was formally appointed as Maximian's
caesar. He adopted Diocletian's
nomen (family name) "Valerius", and, being equated with Maximian, also took on "Herculius". His given command consisted of
Gaul,
Britannia and possibly
Hispania.
Diocletian, the eastern
augustus, in order to keep the balance of power in the
imperium, elevated
Galerius as his
caesar, possibly on 21 May 293 at
Philippopolis (
Plovdiv). Constantius was the more senior of the two
caesares, and on official documents he always took precedence, being mentioned before Galerius. Constantius's capital was to be located at
Augusta Treverorum (
Trier). Constantius's first task on becoming
caesar was to deal with the
Roman usurper Carausius who had declared himself emperor in Britannia and northern Gaul in 286. Carausius was then assassinated by his
rationalis (finance officer)
Allectus, who assumed command of the British provinces until his death in 296. Constantius spent the next two years neutralising the threat of the
Franks who were the allies of Allectus, as northern Gaul remained under the control of the British usurper until at least 295. He also battled against the
Alamanni, achieving some victories at the mouth of the
Rhine in 295. Administrative concerns meant he made at least one trip to Italy during this time as well. did he assemble two invasion fleets with the intent of crossing the
English Channel. The first was entrusted to
Julius Asclepiodotus, Constantius's long-serving
Praetorian prefect, who sailed from the mouth of the
Seine, while the other, under the command of Constantius himself, was launched from his base at Bononia. The fleet under Asclepiodotus landed near the
Isle of Wight, and his army encountered the forces of Allectus, resulting in the defeat and death of the usurper. Constantius in the meantime occupied
Londinium (
London), saving the city from an attack by
Frankish mercenaries who were now roaming the province without a paymaster. Constantius massacred all of them. Constantius remained in Britannia for a few months, replaced most of Allectus's officers, and the British provinces were probably at this time subdivided along the lines of Diocletian's other administrative reforms of the Empire. The result was the division of
Britannia Superior into
Maxima Caesariensis and
Britannia Prima, while
Flavia Caesariensis and
Britannia Secunda were carved out of
Britannia Inferior. He also restored
Hadrian's Wall and its forts. Later in 298, Constantius fought in the
Battle of Lingones (
Langres) against the
Alemanni. He was shut up in the city, but was relieved by his army after six hours and defeated the enemy. He
defeated them again at Vindonissa thereby strengthening the defences of the
Rhine frontier. In 300, he fought against the
Franks on the Rhine frontier, and as part of his overall strategy to buttress the frontier, Constantius settled the Franks in the deserted parts of
Gaul to repopulate the devastated areas. Nevertheless, over the next three years the Rhine frontier continued to occupy Constantius's attention. The campaign was avidly pursued by
Galerius, who noticed that Constantius was well-disposed towards the
Christians, and who saw it as a method of advancing his career prospects with the aging Diocletian. Of the four Tetrarchs, Constantius made the least effort to implement the decrees in the western provinces that were under his direct authority, limiting himself to knocking down a handful of churches.
Eusebius denied that Constantius destroyed Christian buildings, but
Lactantius records that he did. In 304, Maximian met with Galerius, probably to discuss the succession issue and Constantius either was not invited or could not make it due to the situation on the Rhine. by the end of 304 Galerius had convinced Diocletian (who in turn convinced Maximian) to appoint Galerius's nominees
Severus and
Maximinus as
caesares. Constantius, notionally the senior emperor, ruled the western provinces, while Galerius took the eastern provinces. Constantine, disappointed in his hopes to become a
caesar, fled the court of Galerius after Constantius had asked Galerius to release his son as Constantius was ill. Constantine joined his father's court at the coast of Gaul, just as he was preparing to campaign in Britain. In 305, Constantius crossed over into Britain, travelled to the far north of the island and launched a military expedition against the
Picts, claiming a victory against them and the title
Britannicus Maximus II by 7 January 306. After retiring to
Eboracum (
York) for the winter, Constantius had planned to continue the campaign, but on 25 July 306 he died. As he was dying, Constantius recommended his son to the army as his successor; consequently,
Constantine was declared emperor by the legions at York. ==Family==