Tiberius II Constantine

Tiberius rose through the Byzantine court until 574, when Justin II — in a brief window of lucidity during recurring mental collapse — named him caesar and adopted him outright. The promotion was survival politics: someone had to steady the ship. In 578 the dying Justin elevated him to augustus, making them co-emperors for a fortnight before Tiberius inherited sole rule. He governed as Constantine, the name he took at accession. His reign was defined by grinding war: Persians pressing from the east, Avars raiding from the north. He died in office on 14 August 582, four years into the job.