On the death of the Western emperor Honorius, Theodosius II, the last remaining ruler of the Theodosian dynasty, did not immediately announce a successor.

His praetorian prefect was slain in Gaul by an uprising of the soldiery at Arles,[2] and Bonifacius, comes of the Diocese of Africa, held back the grain fleet destined to Rome.

[3] "The events of Johannes' reign are as shadowy as its origins," writes John Matthews, who then provides a list of the ruler's known actions in a single paragraph.

After some skirmishing, Placidia, regent to her son, and Aëtius came to an agreement that established the political landscape of the Western Roman Empire for the next thirty years.

[2] The historian Adrian Goldsworthy writes that "it took a hard-fought campaign by strong elements of the East Roman army and navy, in addition to a fair dose of betrayal," to defeat Joannes.