sius being
allowed to retain possession of Britain. In 290 Maximianus and
Diocletian met at Milan to confer together on the state of the Empire,
after which Diocletian returned to Nicomedia. The Persians soon after
again invaded Mesopotamia and threatened Syria; the Quinquegentiani, a
federation of tribes in the Mauritania Caesariensis, revolted; another
revolt under one Achillaeus broke out in Egypt; another in Italy under
a certain Julianus.

Diocletian thought it necessary to increase the number of his
colleagues in order to face the attacks in the various quarters. On
the 1st of March, 292, or 291, according to some chronologists, he
appointed Galerius as Caesar, and presented him to the troops at
Nicomedia. At the same time Maximianus adopted on his part Constantius
called Chlorus. The two Caesars repudiated their respective wives;
Galerius married Valeria, Diocletian's daughter, adding to his name
that of Valerianus; and Constantius married Theodora, daughter of
Maximianus. Galerius was a native of Dacia, and a good soldier, but
violent and cruel; he had been a herdsman in his youth, for which he
has been styled, in derision, Armentarius. The two Caesars remained
subordinate to the two Augusti, though each of the four was entrusted
with the administration of a part of the Empire. Diocletian kept to
himself Asia and Egypt; Maximianus had Italy and Africa; Galerius,
Thrace and Illyricum; and Constantius had Gaul and Spain. But it was
rather an administrative than a political division. At the head of the
edicts of each prince were put the names of all the four, beginning
with that of Diocletian.

Diocletian resorted to this arrangement probably as much for reasons
of internal as of external policy. For nearly a hundred years before,
ever since the death of Commodus, the soldiers had been in the habit
of giving or selling the imperial crown, to which any general might
aspire. Between thirty and forty emperors had been thus successively
made and unmade many of whom only reigned a few months. By fixing upon
four colleagues, one in each of the great divisions of the Empire,
each having his army, and all mutually checking one another,
Diocletian put a stop to military insolence and anarchy. The Empire
was no longer put up to sale, the immediate and intolerable evil was
effectually cured, though another danger remained, that of disputes
and wars between the various sharers of the imperial power; still it
was a smaller d