In the sixty-fifth year of his life, Roman Emperor Lucius Septimius Severus came under a deathly illness in the north of Britannia during his planning to defeat the Picts in Caledonia. His sons Bassianus, nicknamed “Caracalla” after the Gallic cloak he wore, and Geta were with him. Severus had named Caracalla his co-ruler since 198, and the balance of power seemed effective. He planned for it to continue with Caracalla and Geta becoming co-emperors upon his death. As Severus lay dying, however, he thought back over his life and determined that his advice of “Be harmonious” was ultimately foolish. Men needed to work for themselves, as Severus had done.
Severus amended his will to give his blessing for the ruler of Rome to whoever conquered Caledonia. While the wording was specifically vague and anyone could have done it, he told first his son Caracalla to achieve the deed. If Geta were able to do it, then he would be emperor, causing jealousy that spurred Caracalla to act. Upon Severus’ death, Caracalla rallied his father’s armies and stormed the Highlands at the cost of many Roman lives. The campaign was brutal on both sides, but the guerilla tactics of the Picts were undercut by their limited food resources from Roman domination in the central lowlands and coast under Severus. In 213, Caracalla was proclaimed fully King of Britain and returned to a triumph in Rome where he would be named emperor. Geta attempted to rise in his own power, but Caracalla “promoted” him to proconsul of the new province.
While there was little treasure and the triumph was minor, the expansion proved a boon for Roman morale along with a fresh trade in slaves and space allowing new colonies for veterans. Caracalla raised an arch bearing his father’s dying words, “Conquer, always conquer.” He expanded citizenship to all free men in Rome, causing a leap in tax revenue that he used to build popularity with his armies, though he refused to grant them “luxuries” that he himself had not enjoyed while campaigning in Caledonia. With a force tempered in discipline and made loyal by pay raises, Caracalla marched on Parthia, exploiting a civil war that had raised Artabanus IV to king. They met in battle at Nisibis, and Artabanus was narrowly defeated. Infighting had weakened the local vassals, and Caracalla gained their allegiance by promising protection from raiding nomads.
Upon his return to Rome, Caracalla settled to construction projects and unified his empire while adapting his auxiliaries to include the mounted archers of the East. Though he had two surviving sons, he continued his father’s tradition of naming the next emperor to be him who conquered new lands. Investment in campaigns became a central point of the Roman economy, outfitting Gothic mercenaries and legionaries to march on new regions. The move proved to be deadly for Rome: hyperinflation led to starvation and mass thievery while ineffectual invasions weakened the borders. With civil unrest skyrocketing, the wealthy who had already organized armies turned to warlords, and the empire broke up shortly after Caracalla’s death.
Emperor of Britain and Gaul Constantine would build a haven of stability in the fourth century as he established his capital of Constantinkêr at Eboracum (York). Other, shorter-lived empires would be forged, but few would last. Existing as a series of feudal states in a dark age, the Mediterranean world would be fought over by various waves of Germanic and Nordic conquerors, eventually being re-forged into an expansive Muslim Empire.
In reality, Severus gave his sons the dying advice of "Be harmonious, enrich the soldiers, and scorn all other men." Caracalla would kill Geta soon thereafter and lead an inconsequential campaign in Germany before showering the army with luxuries at the new taxpayers’ expense and marching on Parthia, where he would retreat from Artabanus IV and be killed while urinating by a discontent officer.