Johannes or Joannes, (Flavius Ioannes Augustus)
On the death of the Western Emperor Honorius (August 15th, 423), Theodosius II, his co-emperor in the East hesitated in announcing his uncle's death. In the interregnum, Honorius's patrician at the time of his death, Castinus, elevated Johannes as emperor. Theodosius II refused him any sort of recognition.
Johannes was a primicerius notariorum or senior civil servant at the time of his elevation. Procopius praised him as "both gentle and well-endowed with sagacity and thoroughly capable of valorous deeds." Unlike the Theodosian emperors, he tolerated all Christian sects.
From the beginning, his control over the empire was insecure. In Gaul, his praetorian prefect was slain at Arles in an uprising of the soldiery there. And Bonifacius, Comes of the Diocese of Africa, held back the grain fleet destined to Rome in support of Theodosius.
Little is known about Johannes' reign. He was proclaimed at Rome, but then moved his base of operations to Ravenna. Any hope that he had that he could come to an agreement with the Eastern Emperor, were dashed when Theodosius II elevated the young Valentinian III, first to Caesar, then to co-emperor as an Augustus - that's to say Western Emperor. However, Valentinian was only 5 years old at the time.
Late in 424, Johannes gave to one of his younger and most promising followers, Aëtius, an important mission. Aëtius, who was Governor of the Palace at the time, was sent to the Huns, with whom he had lived as a hostage earlier, to seek military help.
While Aëtius was away, the army of the Eastern Empire left Thessalonica for Italy, and soon camped in Aquileia. Theodosius was ill and remained behind, but Valentinian went along with his mother Galla Placidia under the protection of the Magister Militum, the Alan Ardaburius and his son Aspar. They were also under the guardianship of Candidianus, the general who ten years before had persuaded Honorius to let Placidia marry Athaulf. Candidianus had several victories in northeast Italia. Ardaburius had some success in the marshes of Dalmatia but while sailing to Aquileia he was ship-wrecked on the marshy coast close to Ravenna. He was taken before Johannes but managed to convince him that he was a traitor to Placidia's cause. The eastern army, now under command of Aspar, rushed to Ravenna and after fording the lagoon, took the defences by surprise in early 425.
Johannes was brought to Aquileia where first his hand was cut off, then he was paraded on a donkey in the Hippodrome to the insults of the populace, then after further insults and injuries, he was finally decapitated in June or July 425.
Three days after Johannes's death, Aëtius returned at the head of a substantial Hunnic army. After some half-hearted fighting, Placidia, as regent to her son, and Aëtius came to an agreement. The Huns were paid off and sent home, while Aëtius received the position of magister militum (commander-in-chief of the Roman army).