Res Gestae
Ammianus Marcellinus
Ammianus Marcellinus. Ammianus Marcellinus, with an English translation, Vols. I-III. Rolfe, John C., translator. Cambridge, MA; London: Harvard University Press; W. Heinemann, 1935-1940 (printing).
Thereupon Licinius and Valens, believing that Constantine (as turned out to be the case), in order to follow up his advantage, would advance farther in the direction of Byzantium, turned aside and made their way towards Beroea.[*](A town of Thrace; cf. Amm. xxvii. 4, 12; xxxi. 9, 1.) As Constantine was eagerly pushing on, he learned that Licinius had remained behind him; and just then, when his men were worn out from fighting and marching, Mestrianus was sent to him as an envoy, to propose
Then Constantine, having returned to Serdica, arranged with Licinius, who was elsewhere, that Crispus and Constantinus, sons of Constantine, and Licinius, son of Licinius, should be made Caesars, and that thus the rule should be carried on in harmony by both emperors. Thus Constantine and Licinius became colleagues in the consulship.[*](In 319.)
In the regions of the Orient, while Licinius and Constantine were consuls, Licinius was stirred by sudden madness and ordered that all the Christians should be driven from the Palace.[*](Orosius uses the same language.) Soon war flamed out again between Licinius himself and Constantine.
Also, when Constantine was at Thessalonica, the Goths broke through the neglected frontiers, devasted Thrace and Moesia, and began to drive off booty. Then because of fear of Constantine and his check of their attack they returned their prisoners to him and peace was granted them. But Licinius complained of this action as a breach of faith, on the ground that his function had been usurped by another.
Finally, by using sometimes humble entreaties and sometimes arrogant threats, he aroused the deserved wrath of Constantine, During the interval before the civil war began, but while it was in preparation, Licinius
Now peace was broken by consent of both sides; Constantine sent Crispus Caesar with a large fleet to take possession of Asia, and on the side of Licinius, Amandus opposed him, likewise with naval forces.