537–553), also known as John the Sanguinary, was the nephew of the rebel Vitalian and was an Eastern Roman general under Justinian I (r. 527–565), who was active in the Gothic War in Italy and against the Gepids in the western Balkans.

[1] In 537 John sailed from Constantinople to Italy with 8,000 Thracian troops to reinforce the army of Belisarius who engaged in the Gothic War against the Ostrogoths of King Vitiges.

When the latter arrived to besiege Florence, the general at the head of the garrison of Florence, Justinus, asked for help from the imperial commanders in Ravenna, who intervened in force forcing Totila to lift the siege by retreating in the direction of Mugello, where he routed the imperial army due to the false news of the killing by one of its bodyguards of John, which panicked the Byzantine army.

John fled to Rome, where he took refuge and remained for the next two years, until 544, when he was replaced by Bessas by order of Belisarius, who had returned to Italy.

According to the Secret History of Procopius, Theodora did not want Justina to marry so John, by marrying her, would have attracted the hatred of the empress, to the point that John, fearing that Theodora could order Antonina (Belisarius's wife) to kill him, when he returned to Italy he was careful not to reach Belisarius and his wife in Rome.

Narses reached Ravenna in the summer of 552, and within a year was able to break the resistance of the last Ostrogothic king, Teia, and to put an end to the war (late 552 or early 553).