The Death of Gratian
Gratian appeared to make a good decision by bringing Theodosius into the fold as his new emperor finally made peace with the Goths. Gratian himself was initially an energetic leader but soon preferred the trappings of power to the tedium of governance; this is one of the reasons why he promoted Theodosius in the first place (although some historians believe he was ‘forced’ into it by the army).
After the Battle of Adrianople, Gratian made the mistake of using a group of Alans as his personal bodyguard and dressing as a Scythian warrior. His conduct angered the soldiers and a general named Magnus Maximus started a revolt in Britain and invaded Gaul. Gratian was in Paris at the time, and when his men deserted him, he was forced to flee to Lyon. However, the governor handed him over to a rebel general named Andragathius and Gratian was executed on 25 August, 383. Now, Theodosius was unquestionably the Roman Emperor in the East, and he promoted his son, Arcadius, to the rank of co-emperor upon the death of Gratian.
Theodosius Takes it All
Maximus continued his march to Italy in an attempt to overthrow Valentinian II who was only 12-years old at the time. However, Theodosius saved the day by sending his general, Flavius Bauto, to help the young Emperor with a powerful army. After negotiations, Theodosius and Valentinian II agreed to allow Maximus to become co-emperor in the West in 384.
Theodosius was unable to do anything more to combat the rise of Maximus because he lacked the resources to defeat the enemy and secure his borders. For his part, Maximus was a popular emperor and was notorious for executing heretics. He created an edit in 387 or 388 which condemned Christians for burning down a synagogue; an act which led the Bishop of Milan, Ambrose, to declare: “the emperor has become a Jew.” It was not this edict that led to his downfall. Instead, Maximus got greedy and wanted sole leadership, so he ousted Valentinian II who fled to the court of Theodosius in 387.
At that point, Theodosius was in a much stronger position. He had successfully negotiated peace with Persia, so he no longer had to spend much so time and resources on his eastern frontier. He finally had the power, and an excuse, to deal with Maximus and he began his campaign in July 388. Theodosius defeated the usurper who was executed on 28 August, 388 after surrendering at Aquileia. Maximus’ son, Flavius Victor, was also murdered.
Theodosius was de facto emperor in the West as Valentinian II was little more than a figurehead with a Frankish general named Arbogast as the real power under Theodosius’ orders. Valentinian was present when his friend, Harmonius, was murdered for allegedly taking bribes. The young emperor finally grew tired of being dominated and formally dismissed Arbogast when the Frank forbade him to lead Gallic armies into Italy.
Arbogast tore the order up in public and on 15 May 392, Valentinian II was found hanged in Vienne. Arbogast claimed it was suicide but sources such as sixth-century writer, Zosimus, believe that the general either murdered the emperor himself or paid a member of the Praetorian Guard to do so. Either way, Theodosius was now the Emperor of West and East.