The diocese was established after the reforms of
Diocletian and
Constantine I in c. 314. In the year 407, the Rhine frontier was breached, and much of Gaul lost to barbarian tribes temporarily. Roman control over most of Gaul and the Rhineland was restored until the death of
Valentinian III in 455. The territory remaining in Roman hands after the 450s was in the south in the Auvergne and Provence until ceded in 475 and in the northwest, the so-called "
Domain of Soissons". After its fall to the
Franks in 486 and the end of Roman administration in northern Gaul, the diocese can be said to have
de facto ended. == Further reading ==