When Ottoman troops commanded by Sultan Mehmet II (1432-1481) eventually entered Istanbul on May 29, 1453, following a 53-days siege, and effectively ended the Eastern Roman Empire, which started to be called Byzantium Empire long after its end, perhaps no party in neither side were aware that the conquest would have such wide-ranging and long-lasting repercussions in the history of the world, particularly of the Near East and the Mediterranean.
Istanbul, whose history dates back to the seventh century B.C, as Byzantion that was formed as a trade colony by Megarians from the Greek peninsula, emerged as a world city when it was re-founded by Roman Empire Constantine Great, as New Rome in 324. As a city with its natural port and a strategic and unique location at the conjunction of the Black Sea and the Mediterranean, through the Aegean Sea and Sea, and continents of Asia, Europe and Africa. For over a thousand years afterward, it was the capital Eastern Roman Empire. Which is unique in world history for no other city has such a continuous imperial history. Moreover, for much of its thousand years of empire was the largest, most prosperous and most cultured city in Europe, a treasure-house of the statues and manuscripts of the classical past, and the seat of the Greek Orthodox Ecumenical Patriarchate.
Istanbul that came to be also known as Basileuousa Tov Poleov (Queen of Cities), Rumiyyat al-Kubra (the Great City of Romans), and Asitane (Threshold) in different languages turned to `the city of the world’s desire.’ Against this background, it endured numerous attacks and sieges by Slavs (540, 559, 581), Persians and Avars (626), Arabs (669-679 and 717-718), Bulgarians (813, 913 and 924) and Russians (four times between 860 and 1043), from which it rose victorious mostly thanks to her thick walls, built between 411- 422 AD and streamed distance of six kilometers (over 3.7 miles) from the Golden Horn to the Sea of Marmara and skillful Eastern Roman diplomacy. It, however, never recovered from its sack by the fourth crusade in 1204, organized by Catholic Venice. After the city re-conquered by Eastern Roman Empire in 1261, repeated defeats of the empire by the Muslim army, and civil wars between rival emperors, had reduced the city’s population from a peak of 400,000 inhabitants to about 50,000 Greeks – or `Romans,’ as they called themselves. In 1453, before the conquest, Istanbul, merely a collection of small towns separated by farms and orchards, was far from its glorious and rich heydays.
Fortunately for Istanbul, nevertheless, its conqueror, Sultan Mehmet II, appreciated its beauty, location and role it could play in transforming the state he ruled into an empire. He knew Istanbul had to be restored to its splendid days if Ottomans wanted to expand. This required more than an immerse work of construction the sultan immediately initiated after the conquest. Re-populating Istanbul was what he deemed necessary if the city to become an imperial city. To this end, apart from the Turkish population who were brought or encouraged to move to Istanbul, Greeks, Armenians and Jews, both from within and outside of Ottoman borders, were encouraged to settle in Istanbul in return certain of social and economic privileges, including assuming positions in the imperial bureaucracy and the Ottoman court.
Furthermore, he revived Greek Orthodox Ecumenical Patriarchate in Istanbul by appointing Gennadios Scholarius, one of the most respected and learned Orthodox cleric, as patriarch in 1454 and administrative, judicial, financial and religious autonomy. Similarly, he established the Armenian Patriarchate in Istanbul in 1461, with Hovakim I being the first patriarch. Italians were the other major Christian constituent of the imperial capital. While the Genoese colony at the Galata district of Istanbul remained untouched during the siege and after the conquest of the city, its population and prosperity soared significantly after more Genoese and Venetians moved into the city after the conquest of Genoese and Italian possessions by Ottomans in the Black Sea and the Aegean Sea. Furthermore, Jews of Europe who left the intolerance, systematic discrimination, pogroms and forceful religious conversions to Christianity found more than a safe haven in new Istanbul. They started to flourish as blacksmiths, carpenters, tax farmers, bankers and doctors. Fruits of Mehmet’s ambition over Istanbul and its smart policy became visible as the 1477 census indicated. In Istanbul, according to the census, 9,486 houses inhabited by Muslims; 3,743 houses inhabited by Greeks; 1,647 houses inhabited by Jews; 434 houses inhabited by Armenians; 384 houses inhabited by Turkish speaking Greek Orthodox; 332 houses inhabited by various European nationalities, mostly Italian; 267 houses inhabited by Christians from the Crimea, and 31 houses inhabited by gypsies. Istanbul had turned into the only multinational and capital in Europe, in whose streets, Turkish, Persian and Arabic Greek, Armenian, Italian, Albanian, Bulgarian and Serbian were spoken by its residents and one of the wealthiest and well-maintained cities of the word.
 For a detailed study over major sieges and attacks against Istanbul in the course of its history, see Murat Aslan and Turan Kacan eds.,Byzantion’dan Constantinopolis’e Istanbul Kuşatmaları,(Istanbul: Ιstanbul Research Institute,2017)
 Philip Mansel, Constantinople: City of World’s Desire (London: John Murray, 1995),1-3.
 Omer Lutfi Barkan “Essai sur les données statistiques des registres de recensements dans l’Empire Ottoman aux XV’e et XVI’e siècles.” Journal of the Economic and Social History of the Orient, 1, 1957, pg. 9-36