Lucius Septimius Bassianus was the elder of two sons of the emperor Septimius Severus. His cognomen Bassianus stems from his maternal grandfather, Gaius Julius Bassianus who was a priest of Heliogabalus, the patron god of Emesa, Syria. He was born in April AD 188, in the city of Lugdunum (Lyon, France) while his father (Severus) was governor of Gaul during the reign of Commodus.
When his father won the civil war following the assassination of Commodus (c. 193), Bassianus was declared Caesar (heir) and renamed Marcus Aurelius Antoninus in order to establish the Severan reign as legitimate heirs to the popular and adoptive Antonine dynasty.
The name Caracalla emerged from the style of cloak that he wore and later made popular throughout the empire. While it distinguishes his identity in a historical context, much like the name Caligula as a substitute for the third princeps Gaius, it should be considered little more than a nickname as it was not used in any official capacity.
The appointment of Caracalla as Caesar to his father negated a previous deal with the Roman governor of Britain, Clodius Albinus. Civil war was renewed, but Severus proved superior to his rival and defeated him at the battle of Lugdunum (Lyons, France) in February AD 197. Cementing the dynastic intentions, the ten year old Caracalla was named co-Augustus the following year and younger son Geta (by only 11 months) was named Caesar. In 202, Caracalla was married to Publia Fulvia Plautilla, the daughter of Praetorian Prefect C. Fulvius Plautianus, though the marriage proved to be politically disastrous.
Caracalla despised his wife while he his brother Geta and mother Julia Domna distrusted the growing power and influence of Plautianus. As a result, Plautianus may have sensed his own impending fall and plotted the overthrow of Severus or was perhaps simply a victim of the political machinations of the Severan family. He was accused of treason and executed in January, 205 while Plautilla (and her brother) were sent into exile.
After the death of Plautianus, both Caracalla and Geta began to aggressively assert their own authority and individual identities. According to Cassius Dio, "They outraged women and abused boys, they embezzled money, and made gladiators and charioteers their boon companions, emulating each other in the similarity of their deeds, but full of strife in their rivalries; for if the one attached himself to a certain faction, the other would be sure to choose the opposite side. And at last they were pitted against each other in some kind of contest with teams of ponies and drove with such fierce rivalry that Antoninus fell out of his two-wheeled chariot and broke his leg."
Severus recognized the danger of the rivalry and organized a military campaign in northern Britain in order to reinvigorate a growing idleness in the legions and also to occupy his sons in an endeavor of higher responsibility. In his middle 60's and in poor personal health, Severus gave command to Caracalla while Geta was appointed to co-Augustus and given authority over administrative duties.
The campaign itself, though hampered by the rough terrain of Caledonia, was probably more successful than Severus' attempt to bring his sons together. The rivalry continued more bitter than ever, and Severus feared for Geta's life. However, his health had rapidly deteriorated since the arrival of the family in Britain and little could be done to reconcile the future emperors. On February 4, 211 Severus died in Eboracum (York) and left the empire to the near 23 year old Caracalla and 22 year old Geta.
The new joint emperors returned to Rome shortly after their father's death but the relationship continued as it always had. Caracalla vied for ultimate authority and attempted to marginalize the position of Geta; who sought imperial equality. Distrust by both parties led to cooperative failure on decisions of policy, political appointments and general authority. The rivalry was beyond reconciliation; the two sides unable to find a tenable solution. Ultimately, Geta was murdered in December, 211 and in a systematic purge of his supporters, contemporary historian Cassius Dio claimed that some 20,000 people were put to death.