Middle Ages

In the seventh century, Emperor Heraclius adopted Medieval Greek as the official language of the Byzantine Empire. Greeks continued to live around the Levant, Mediterranean and Black Sea, maintaining their identity among local populations as traders, officials, and settlers. Soon afterwards, the Arab-Islamic Caliphate seized the Levant, Egypt, North Africa and Sicily from the Byzantine Greeks during the Byzantine–Arab Wars. The Greek populations generally remained in these areas of the Caliphate and helped translate ancient Greek works into Arabic, thus contributing to early Islamic philosophy and science (which, in turn, contributed to Byzantine science).

Fall of Byzantium and exodus to Italy

After the Byzantine–Ottoman Wars, which resulted in the fall of Constantinople in 1453 and the Ottoman conquest of Greek lands, many Greeks fled Constantinople (now Istanbul) and found refuge in Italy. They brought ancient Greek writings that had been lost in the West, contributing to the Renaissance. Most of these Greeks settled in Venice, Florence, and Rome.

Fall of the Empire of Trebizond and exodus to Russia and Georgia

Between the fall of the Empire of Trebizond to the Ottomans in 1461 and the second Russo-Turkish War in 1828–29, thousands of Pontic Greeks migrated (or fled) from the Pontic Alps and eastern Anatolia to Georgia and other southern regions of the Russian Empire, and (later) the Russian province of Kars in the South Caucasus. Many Pontic Greeks fled their homelands in Pontus and northeastern Anatolia and settled in these areas to avoid Ottoman reprisals after supporting the Russian invasions of eastern Anatolia in the Russo-Turkish Wars from the late 18th to the early 20th century. Others resettled in search of new opportunities in trade, mining, farming, the church, the military, and the bureaucracy of the Russian Empire.^[11]

Ottoman Empire

Greeks spread through many provinces of the Ottoman Empire and took major roles in its economic life, particularly the Phanariots (wealthy Greek merchants who claimed noble Byzantine descent during the second half of the 16th century). The Phanariots helped administer the Ottoman Empire's Balkan domains in the 18th century; some settled in present-day Romania, influencing its political and cultural life. Other Greeks settled outside the southern Balkans, moving north in service to the Orthodox Church or as a result of population transfers and massacres by Ottoman authorities after Greek rebellions against Ottoman rule or suspected Greek collaboration with Russia in the Russo-Turkish wars fought between 1774 and 1878. Greek Macedonia was most affected by the population upheavals, where the large, indigenous Ottoman Muslim population (often including those of Greek-convert descent) could form local militias to harass and exact revenge on the Greek-speaking Christian Orthodox population; this often forced the inhabitants of rural districts, particularly in the more vulnerable lowland areas, to abandon their homes.^{[citation needed]}

A larger-scale movement of Greek-speaking peoples in the Ottoman period was Pontic Greeks from northeastern Anatolia to Georgia and parts of southern Russia, particularly the province of Kars Oblast in the southern Caucasus after the short-lived Russian occupation of Erzerum and the surrounding region during the 1828–29 Russo-Turkish War. An estimated one-fifth of Pontic Greeks left their homeland in the mountains of northeastern Anatolia in 1829 as refugees, following the Tsarist army as it withdrew back into Russian territory (since many had collaborated with—or fought in—the Russian army against the Muslim Ottomans to regain territory for Christian Orthodoxy). The Pontic Greek refugees who settled in Georgia and the southern Caucasus assimilated with preexisting Caucasus Greek communities. Those who settled in Ukraine and southern Russia became a sizable proportion of cities such as Mariupol, but generally assimilated with Christian Orthodox Russians and continued to serve in the Tsarist army.

In 1788, Ali Pasha of Ioannina destroyed Moscopole. This predominantly ethnic Aromanian settlement historically had an important Greek influence.^[12] This is why some members of the Aromanian diaspora that settled in places such as Vienna in Austria have been considered as Greeks and part of a Greek diaspora as well.^[13]

19th century

During and after the Greek War of Independence, Greeks of the diaspora established the fledgling state, raised funds and awareness abroad and served as senior officers in Russian armies which fought the Ottomans to help liberate Greeks under Ottoman subjugation in Macedonia, Epirus, and Thrace. Greek merchant families had contacts in other countries; during the disturbances, many set up home bases around the Mediterranean (notably Marseilles in France, Livorno, Calabria and Bari in Italy and Alexandria in Egypt), Russia (Odesa and St. Petersburg), and Britain (London and Liverpool) from where they traded (typically textiles and grain). Businesses frequently included the extended family, and they brought schools teaching Greek and the Greek Orthodox Church.^[14] As markets changed, some families became shippers (financed through the local Greek community, with the aid of the Ralli or Vagliano Brothers). The diaspora expanded across the Levant, North Africa, India^[15] and the US.^[16] Many leaders of the Greek struggle for liberation from Ottoman Macedonia and other parts of the southern Balkans with large Greek populations still under Ottoman rule had links to the Greek trading and business families who funded the Greek liberation struggle against the Ottomans and the creation of a Greater Greece.

The terrible devastation of the island of Chios in the 1822 massacre caused a great dispersion of the islanders, leading to the creation of a specific Chian diaspora.

After the Treaty of Constantinople, the political situation stabilised; some displaced families returned to the newly independent country to become key figures in cultural, educational and political life, especially in Athens. Financial assistance from overseas was channeled through these family ties, providing for institutions such as the National Library and sending relief after natural disasters.

20th century

During the 20th century, many Greeks left the traditional homelands for economic and political reasons; this resulted in large migrations from Greece and Cyprus to the United States, Australia, Canada, Brazil, The United Kingdom, New Zealand, Argentina, The United Arab Emirates, Singapore, Germany, Norway, Belgium, Georgia, Italy, Armenia, Russia, Philippines, Chile, Mexico and South Africa, especially after World War II (1939–45), the Greek Civil War (1946–49) and the Turkish Invasion of Cyprus in 1974.^[17]

After World War I, most Pontian and Anatolian Greeks living in Asia Minor (modern-day Turkey) were victims of Muslim Turkish intolerance for Christians in the Ottoman Empire. More than 3.5 million Greeks, Armenians, and Assyrians were killed in the regimes of the Young Turks and Mustafa Kemal, from 1914 to 1923.^[18] Greeks in Asia Minor fled to modern Greece, and the Russian Empire (later the USSR) was also a major destination.

After the Greek Civil War, many communist Greeks and their families fled to neighboring Yugoslavia, the USSR and the Soviet-dominated states of Eastern Europe (especially Czechoslovakia). Hungary founded a village (Beloiannisz) for Greek refugees, and many Greeks were resettled in the former Sudeten German region of northern Czechoslovakia around Krnov (Jägerndorf). Sweden also admitted large numbers of Greeks, and over 17,000 Greek-Swedish descendants live in the country. Although many immigrants later returned to Greece, these countries still have a number of first- and second-generation Greeks who maintain their traditions.^[17]

With the fall of Communism in eastern Europe and the USSR, Greeks of the diaspora immigrated to modern Greece's main urban centers of Athens, Thessaloniki, and Cyprus; many came from Georgia.^[17]

Pontic Greeks are Greek-speaking communities originating in the Black Sea region, particularly from the Trebizond region, the Pontic Alps, eastern Anatolia, Georgia, and the former Russian south-Caucasus Kars Oblast. After 1919–23, most of these Pontic Greek and Caucasus Greek communities resettled in Greek Macedonia or joined other Greek communities in southern Russia and Ukraine.