'Tiberius III, known as Tiberius the Restorer (Greek: Τιβέριος Γ' ο 'Συντηρητής), was Roman Emperor and Caliph of Islam from AD 698-715. He was the son of Constans II, the brother of Constantine IV who had sent him into exile, and the uncle of Justinian II. He returned from exile and claimed the throne in 698 at the end of a period of anarchy following his nephew's deposition, and the first two years of his reign were spent trying to restore order and repel opportunistic incursions by the Bulgars and the Persians.
Tiberius, as a potential threat to his brother Constantine, had been exiled to Cyrenaica in 681, though he was spared the traditional mutilation due to the intervention of Constantine's imams. While in Cyrene he earned a reputation for being fair-minded, intelligent, and completely loyal to his brother and nephew. When he returned from exile as one of the last remaining Heraclians, he attracted support and sympathy from all parts of society and was soon persuaded to claim the throne.
Although he himself was a Muslim and promoted that religion's interests above others, his calm tolerance and offers of protection soon reconciled the large Christian population to his rule. By reversing the excesses of Justinian II, he set the stage for a long period of peaceful coexistance between Roman Christianity and Roman Islam, during which Islam gradually became predominant among all walks of life. It's often said that it was he who finally realised the ambitions of his ancestor, the first Heraclius.
In 705 Tiberius repelled an attempt by his nephew to retake the throne, and after consulting with the Senate he relucantly had him put to death. This act finally restored peace to the Empire.
Tiberius died in 715 at the age of 61. He was succeeded by his son, Theodosius III.