The joint rule with Tiberius II (his regent), 26 September 574 - 5 October 578 A.D.
Justin II was selected by his uncle, Emperor Justinian, to be his successor. Justinian's successful restoration of former Imperial territory had been an enormous burden on the financial resources of the state and Justin was unable to hold the territory. A few years into Justin's reign most of Italy was lost to the Lombards and the Visigoths retook areas in Spain. On the Eastern frontier, he refused to pay tribute to the Sassanid ruler Khusru I resulting in a protracted war. The burdens of office took their toll on Justin and he began to show clear signs of insanity. In 574, Tiberius was appointed as his regent and Caesar. Nine days prior to Justin's death, Tiberius was promoted to Augustus and co-emperor.