Gessius Bassianus Alexianus was born in c.208/9 AD at Phoenicia-Arca Caesarea. He was the son of Marcus Julius Gessius Marcianus and Julia Avita Mamaea, making him the cousin of Elagabalus and part of the ruling Severan family. Not much is written about his youth, but it is documented he accompanied his cousin to Rome when Elagabalus was proclaimed emperor in 218. This characters are in many Roman Coins.
While living in Rome under the rule of Elagabalus, Alexianus remained virtually unknown. The citizens of Rome became increasingly intolerant of the bizarre behavior and rituals of Elagabalus over the years, forcing Julia Maesa, grandmother of Elagabalus, to put pressure on the emperor to adopt his cousin and elevate him to the rank of Caesar on June 26, 221. Alexianus was Maesa’s backup plan to keep the Severan dynasty in power, in the event Elagabalus became increasingly difficult to control. Upon attaining his new title, Alexianus changed his name to Marcus Aurelius Severus Alexander.
Over the next months, Elagabalus became jealous and suspicious of Severus Alexander and attempted numerous times to have his cousin assassinated, to no avail, as he could not find anyone who would support the unstable emperor. At the time, there was a popular superstition going around that the spirit of Alexander the Great was making its way across the land and disappeared crossing the Bosporus. Rumor was that it was going to reappear in Rome in Severus Alexander, making him very popular with the military.
On March 11, 222, Elagabalus made his move and claimed Severus Alexander was sick and near death. The praetorians demanded a meeting in their camp with both Elagabalus and Severus Alexander, finding on their arrival Caesar doing just fine. Elagabalus confronted the praetorian guards and demanded Severus Alexander be stripped of his title, but the guards instead murdered the emperor and his deranged mother, Julia Soaemias. Two days later, at the age of 13 or 14, Severus Alexander was proclaimed emperor – the youngest until the reign of Gordian III.
Severus Alexander relied heavily on his mother and grandmother, along with a council of 16 senators, one of them being the historian Cassius Dio. Roman life began to return to the way it was before the arrival of the Syrians – the Emesa Stone was returned to the East, the temple to Elagabalus was rededicated to Jupiter Ultor and the religious practices went back to worshipping the Roman gods.
In 225, Severus Alexander married his first wife – Barbia Orbiana. She was the daughter of Seius Sallustius Varius Macrinus, who apparently was elevated to Caesar as part of the arrangement through Julia Mamaea. They didn’t have any children, but their marriage was very compatible. So much so that it was affecting Julia Mamaea’s influence. Combined with the power grab being orchestrated by Sallustius, Mamaea decided to intervene. She had the marriage annulled in 227 and charged Sallustius with treason. Orbiana was banished and Sallustius was executed. Severus Alexander would marry two more times – once to Sulpicia Memmia and another who is unknown completely. These marriages also produced no children.
During the entire reign of Severus Alexander to this point, the Sassanians were becoming a power in the East under King Ardashir I. In 230, the Sassanians invaded Mesopotamia, Nisibis and Carrhae, and heading to Syria. Despite efforts to negotiate, the Sassanians kept pushing onward. The Romans fought back in 232, retaking Mesopotamia and stopping the advancement of the Sassanians, but with heavy losses on both sides. Severus Alexander returned to Rome and was given a triumphal procession in 233, along with the title Persicus Maximus.
Conflict was brewing elsewhere and Severus Alexander and Julia Mamaea found themselves leading their legions to the Rhine region in 234 to battle the Alemanni. The Romans won a quick victory, but Severus Alexander being ever cautious, wanted to buy peace until the rest of his legions could arrive for backup. The troops were greatly angered by this decision as they wanted to eliminate the Alemanni for attacking while their land was undefended dealing with the Sassanians. The soldiers rebelled and declared one of their officers, Maximinus I Thrax, as emperor. Severus Alexander was murdered in his mother’s arms during the mutiny of Legio XXII Primigenia in March 235 near Mainz.