Laz people lived in Tzanica, the area located between the Byzantine and the Lazica. It included several settlements named: Athenae, Archabis and Apsarus; Tzanni were neither subjects of the Romans nor of the king of the Lazica, except that during the reign of the Byzantine emperor Justinian I (r. 527–565) they were subdued, Christianized and brought to central rule. The bishops of the Lazica appointed their priests, seeing they are Christians. Tzanni began to have closer contact with the Greeks and acquired various Hellenic cultural traits, including in some cases the language. From 542 to 562, Lazica was a scene of the protracted rivalry between the Eastern Roman and Sassanid empires, culminating in the Lazic War, where 1,000 Tzanni auxiliaries under Dagisthaeus participated. Emperor Heraclius's offensive in 628 AD brought victory over the Persians and ensured Roman predominance in Lazica until the invasion and conquest of the Caucasus by the Arabs in the second half of the seventh century. As the result of Muslim invasions, the ancient metropolis, Phasis, was lost and Trebizond became the new Metropolitan bishop of Lazica, since then the name Lazi appears the general Greek name for Tzanni. According to Geography of Anania Shirakatsi of the 7th century, Colchis (Yeger in Armenian sources, same as Lazica) was subdivided into four small districts, one of them being Tzanica, that is Chaldia, and mentions Athinae, Rhizus and Trebizond among its cities. From the second half of the eight century the Trebizond area is referred to in Greek sources (namely of Epiphanius of Constantinople) as Lazica. The 10th-century Arab geographer Abul Feda regards city of Trebizond as being largely a Lazian port. In 780, kingdom of Abkhazia incorporated the former territories of Lazica via a dynastic succession, thus ousting the Pontic Lazs (formerly known as Tzanni) from western Georgia; thereafter, the Tzanni lived under nominal Byzantine suzerainty in the theme of Chaldia, with its capital at Trebizond, governed by the native semi-autonomous rulers, like the Gabras family, of possibly "Greco-Laz" or simply Chaldian origin. With the Georgian intervention in Chaldia and collapse of Byzantine Empire in 1204, Empire of Trebizond was established along the southeastern coast of the Black Sea, populated by a large Kartvelian-speaking population. In the eastern part of the same empire, an autonomous coastal theme of Greater Lazia was established. Byzantine authors, such as Pachymeres, and to some extent Trapezuntines such as Lazaropoulos and Bessarion, regarded