Constantius I Chlorus

Constantius I, nicknamed Chlorus (c. 250–306), was a Roman emperor of the Tetrarchy and father of Constantine the Great. A career soldier from Moesia Superior, he rose to become Maximian’s praetorian prefect, divorced Helena to marry Maximian’s daughter Theodora, and in 293 was made caesar of the western provinces.

From Gaul he overthrew the British usurpers Carausius and Allectus and campaigned against the Alamanni and Franks; in the persecution of 303 he only demolished churches. He became augustus in 305 and died at Eboracum in 306, where his army proclaimed Constantine emperor, hastening the Tetrarchy’s collapse.