Marcus Aurelius Severus Alexander, commonly called Alexander Severus, (October 1, 208–March 18, 235) was the last Roman emperor (11 March 222–235) of the Severan dynasty, having succeeded, as heir apparent, his despised second cousin, the eighteen year old Emperor Elagabalus who had been murdered along with his mother by his own guards—and as a mark of contempt, had their remains cast into the Tiber river. He became emperor suddenly when a rumor of Alexander's death had circulated, triggering the assassination. He and his second cousin were both grandsons of the influential and powerful Julia Maesa, who had arranged for Elagabalus' acclaimation by the Legio III Gallica as emperor.
He was in turn assassinated at the hands of his troops after suffering a defeat at arms against the Germanic tribes after first trying diplomacy and bribery, which alienated the legions. His assassination sparked, and is used as the epoch event for, the Crisis of the Third Century—the nearly fifty years of disorder, multiple civil wars between warring claimants to his title, economic chaos, regional rebellions, and various external threats which followed.
When Alexander became emperor, he was young, amiable, well-meaning, and entirely under the dominion of his mother. Julia Mamaea was a woman of many virtues, and she surrounded the young emperor with wise counsellors. She watched over the development of her son's character and improved the tone of the administration. On the other hand, she was inordinately jealous. She also alienated the army by extreme parsimony, and neither she nor her son were strong enough to impose military discipline. Mutinies became frequent in all parts of the empire; to one of them the life of the jurist and praetorian praefect Ulpian was sacrificed; another compelled the retirement of Cassius Dio from his command.
On the whole, however, the reign of Alexander was prosperous until the rise, in the east, of the Sassanids. Of the war that followed there are very various accounts. (Mommsen leans to that which is least favourable to the Romans). According to Alexander's own dispatch to the senate, he gained great victories. At all events, though the Sassanids were checked for the time, the conduct of the Roman army showed an extraordinary lack of discipline. The emperor returned to Rome and celebrated a triumph in 233.
The following year he was called to face German invaders in Gaul, who had breached the Rhine frontier in several places, destroying forts and over-running the countryside. Alexander mustered his forces, bringing legions from the eastern provinces, and crossed the Rhine into Germany on a pontoon bridge. Initially he attempted to buy the German tribes off, so as to gain time. Whether this was a wise policy or not, it caused the Roman legionaries to look down on their emperor as one who was prepared to commit unsoldierly conduct. Herodian says "in their opinion Alexander showed no honourable intention to pursue the war and preferred a life of ease, when he should have marched out to punish the Germans for their previous insolence". These circumstances drove the army to look for a new leader. They chose Gaius Iulius Verus Maximinus, a Thracian soldier who had worked his way up through the ranks.
Following the nomination of Maximinus as emperor, Alexander was slain, (on either March 18 and March 19 235 are the two possibilities), together with his mother, in a mutiny of the Legio XXII Primigenia. These assassinations secured the throne for Maximinus.
The death of Alexander is now recognised as the final nail in the coffin of the principate system established by Augustus and signalled the beginning of the chaotic period known as the Crisis of the Third Century which weakened the empire considerably.
Alexander was the last of the Syrian emperors. Under the influence of his mother, he did much to improve the morals and condition of the people. His advisers were men like the famous jurist Ulpian, the historian Cassius Dio and a select board of sixteen senators; a municipal council of fourteen assisted the urban praefect in administering the affairs of the fourteen districts of Rome. The luxury and extravagance that had formerly been so prevalent at the court were put down; the standard of the coinage was raised; taxes were lightened; literature, art and science were encouraged; the lot of the soldiers was improved; and, for the convenience of the people, loan offices were instituted for lending money at a moderate rate of interest.
In religious matters Alexander preserved an open mind. It is said that he was desirous of erecting a temple to the founder of Christianity, but was dissuaded by the pagan priests.