Herodian (late second, first half third century): Greek historian, author of a History of the Roman Empire since the Death of Marcus Aurelius in which he describes the reign of Commodus (180-192), the Year of the Five Emperors (193), the age of the Severan dynasty (211-235), and the Year of the Six Emperors (238).
The translation was made by Edward C. Echols (Herodian of Antioch's History of the Roman Empire, 1961 Berkeley and Los Angeles) and was put online for the first time by Roger Pearse (Tertullian.Org). The version offered on these pages is hyperlinked and contains notes by Jona Lendering.
Caracalla versus Geta
[4.3.1]  After completing this ceremony of deification for their father, the youths returned to the palace. Open hostility followed, as they nurtured their hatred and hatched their plots. Each did everything in his power to eliminate his brother and secure the empire for himself alone.
[4.3.2] The honored and respected men of the city held divided opinions. Each of the youths privately solicited their support in secret letters, trying to win them by lavish promises. The majority favored Geta, who showed some evidence of a reasonable disposition, since he conducted himself mildly and moderately toward those who visited him, and devoted his time to the more serious pursuits.
[4.3.3] He studied with men respected for their learningnote[An allusion to the cultural cercle of Julia Domna.] and exercised frequently at the wrestling schools and the various gymnasia. Because he was kind and courteous to his associates and had an excellent reputation and good name, he won the friendship and good will of most of the Romans.
[4.3.4] By contrast, Caracalla was harsh and savage in everything he did, scorning the pursuits mentioned above, and pretending a devotion to the military and martial life. Since he did everything in anger and used threats instead of persuasion, his friends were bound to him by fear, not by affection.
As the brothers were now completely at odds in even the most trivial matters, their mother undertook to effect a reconciliation.
[4.3.5] And at that time they concluded that it was best to divide the empire, to avoid remaining in Rome and continuing their intrigues. Summoning the advisers appointed by their father, with their mother present too, they decided to partition the empire: Caracalla to have all Europe, and Geta all the lands lying opposite Europe, the region known as Asia.
[4.3.6] For, they said, the two continents were separated by the Propontic Gulf as if by divine foresight. It was agreed that Caracalla establish his headquarters at Byzantium, with Geta's at Chalcedon in Bithynia; the two stations, on opposite sides of the straits, would guard each empire and prevent any crossings at that point. They decided too that it was best that the European senators remain in Rome, and those from the Asiatic regions accompany Geta.
[4.3.7] For his capital city, Geta said that either Antioch or Alexandria would be suitable, since, in his opinion, neither city was much inferior in size to Rome. Of the Southern provinces, the lands of the Moors, the Numidians, and the adjacent Libyans were given to Caracalla, and the regions east of these peoples were allotted to Geta.
[4.3.8] While they were engaged in cleaving the empire, all the rest kept their eyes fixed on the ground, but Julia cried out: "Earth and sea, my children, you have found a way to divide, and, as you say, the Propontic Gulf separates the continents. But your mother, how would you parcel her? How am I, unhappy, wretched - how am I to be torn and ripped asunder for the pair of you? Kill me first, and after you have claimed your share, let each one perform the funeral rites for his portion. Thus would I, too, together with earth and sea, be partitioned between you."
[4.3.9] After saying this, amid tears and lamentations, Julia stretched out her hands and, clasping them both in her arms, tried to reconcile them. And with all pitying her, the meeting adjourned and the project was abandoned. Each youth returned to his half of the imperial palace.