John (nephew of Vitalian)

John (Latin: Ioannes, Greek: Ίωάννης, fl. 537–553), also known as John the Sanguinary, was a Byzantine general under Justinian I (r. 527–565) and took active part in the Gothic War (535–554) against the Ostrogoths (Goths). He was the nephew of the rebel Vitalian and later in his life, he was married to Justina, the daughter of Justinian's cousin Germanus.

By 537, he had gained a reputation for bravery and command ability. He was tasked to bring supplies and reinforcements to general Belisarius, who was defending Rome from a numerically superior Gothic army. John captured the strategically important city of Ariminum, which forced the Goths to abandon the siege of Rome. Despite his success, he disobeyed Belisarius's orders, and even though Belisarius later saved him in the Siege of Ariminum (538), John refused to thank him. John's insubordination became a focal point in the fracturing Byzantine leadership, leading to the destruction of Milan. In the final part of the Gothic War, he followed Narses and defeated the Goths at Taginae and Mons Lactarius, ending the war.