Flavius Valerius Constantius "Chlorus" ( – 25 July 306), also called Constantius I, was Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname Chlorus () was first popularized by Byzantine-era historians and not used during the emperor's lifetime. After his re-conquering of Roman Britain, he was given the title 'Redditor Lucis Aeternae', meaning 'The Restorer of Eternal Light'. Of humble origin, Constantius had a distinguished military career and rose to the top ranks of the army. Around 289 he set aside Helena, Constantine's mother, to marry a daughter of Emperor Maximian, and in 293 was added to the imperial college by Maximian's colleague, Diocletian. Assigned to rule Gaul, Constantius defeated the usurper Carausius there and his successor Allectus in Britain, and campaigned extensively along the Rhine frontier, defeating the Alamanni and Franks. When the Diocletianic Persecution was announced in 303, Constantius ordered the demolition of churches but did not actively hunt down Christians in his domain. Upon becoming senior emperor in May 305, Constantius launched a successful punitive campaign against the Picts beyond the Antonine Wall. He died suddenly at Eboracum (York) in July the following year. After Constantius's death, the army, perhaps at his own instigation, immediately acclaimed his son Constantine as emperor. This act contributed to the collapse of the Diocletianic tetrarchy, sparking a series of civil wars which only ended when Constantine finally united the whole Roman Empire under his rule in 324. According to the Oxford Classical Dictionary, "Constantinian propaganda bedevils assessment of Constantius, yet he appears to have been an able general and a generous ruler". His descendants, the Constantinian dynasty, ruled the Empire until the death of his grandson Julian the Apostate in 363. Life 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 an Illyrian. He was born in Naissus, Dacia Ripensis, a Roman province on the south bank of the Middle Danube – the empire's frontier – with its capital at Ratiaria (modern Archar). According to the unreliable Historia Augusta he was the son of Eutropius, a