The history of Istanbul during the Ottoman Empire covers the period from the capture of Constantinople by the Turks on 29 May 1453 to the abolition of the Ottoman Empire in 1922 and the transfer of the capital of Turkey to Ankara on 13 October 1923. For almost five centuries Istanbul was the capital of a vast state that took shape in the 14th–16th centuries as a result of the conquest campaigns of the Turkish sultans. The borders of the Ottoman Empire encompassed territories in three parts of the world – Europe, Asia and Africa. Thus, the ancient city on the shores of the Bosphorus once again became a political and economic centre of world importance. Gradually, Istanbul regained its fame as a major hub of international trade. Although the most important trade routes shifted from the Mediterranean to the Atlantic, the Turkish Straits continued to remain a bustling trade artery of the late Middle Ages.
In addition, as the residence of the caliphate, Istanbul acquired the significance of an important religious centre of the Muslim world, incorporating and reworking much from the culture of the Seljuks, Byzantines, Arabs and Persians (from Constantinople, Istanbul inherited the residence of the Ecumenical Patriarch – first among the Orthodox patriarchs of the world). The city represented a miniature model of the Ottoman Empire, with its ethnically and religiously motley population. The Ottoman capital reached its greatest flourishing during the reign of Suleiman the Magnificent, and most of the enthusiastic descriptions of Istanbul by European travellers and diplomats date to the "century of Suleiman". Since the reign of Mehmed III the gradual decline of the Ottoman Empire began, though this did not immediately affect the prosperous Istanbul. But already after Ahmed I almost no large mosques were built in the city, some monumental buildings were erected over decades, whereas riots and revolts multiplied among both the Janissaries and the capital's lower classes. The deterioration of the economic situation led to stagnation in culture and science, as well as to the ever-increasing influence of Western European powers on all spheres of life in the empire and its capital.
Mehmed II's era On 29 May 1453, Turkish forces captured Constantinople. Mehmed II, after allowing his army to plunder the conquered city, entered it through the Charisius Gate (according to other sources, the sultan entered Constantinople only three days later, after the chaos of looting and pogroms had subsided). He ceremoniously proceeded to the city centre and, as a sign of victory over the enemy, rode a white horse into Hagia Sophia, ordering its conversion into a mosque. Much of Constantinople was subjected to thorough plundering, though some areas (Studion and Petrion), monasteries, and churches remained untouched. The city itself, through the gradual transformation of the word "Constantinople" within the phonetic norms of the Turkish language, became popularly known as Istanbul,According to another version, the toponym "Istanbul" phonetically derives from the Greek phrase "eis tin polin," meaning "to the city." It is said that Greeks heading to Constantinople responded thus when asked by Turks where they were going. The Muslim conquerors gave the new name their own etymology, interpreting it as "Islambol" ("Abundance of Islam"). although the Ottomans officially continued to call it Kostantiniyye in the Arabic style for a long time. Later, thanks to the prominence of Greek dragomans, the name "Constantinople" regained widespread use in Ottoman diplomacy (in practice, both toponyms were used concurrently, but in the Christian world, the city continued to be called by its old name).
When dividing the spoils and trophies, Mehmed, per custom, received one-fifth of all that was seized. He settled his share of captives in the Fener district, thus laying the foundation for Istanbul's Greek quarter. Additionally, the inhabitants of Greek villages along the Bosphorus, who formally did not participate in the resistance, escaped captivity and deportation. Over 30,000 Greeks and Latins were sold in the slave markets of Edirne, Bursa, Gallipoli, Ankara, and Philippopolis, though many were redeemed by wealthy relatives (according to other sources, Constantinople had about 70,000 inhabitants at the time of the conquest, of whom 50,000–60,000 were sold into slavery or deported, while 10,000–20,000 remained in the city as free citizens). The bailo of the Venetian colony, Minotto, his son, and other prominent Venetians, as well as the Catalan consul and several of his compatriots, were executed. Lucas Notaras, whom Mehmed intended to appoint as the new prefect of Ottoman Constantinople, was executed for refusing to give his son to the sultan as a lover. However, other active defenders of Constantinople managed to escape, including Cardinal Isidore of Kiev, Archbishop Leonard of Chios, two of the three Bocchiardi brothers, and the Grand Logothete George Sphrantzes. Mehmed ordered the walls of Galata to be demolished and its moat filled, and all weapons were confiscated from the Genoese there. However, he guaranteed the enclave's safety, allowed it to retain its Christian character, and forbade Turks from settling there (in Galata, two Franciscan monasteries and several churches continued to hold Mass; for this reason, Turks long considered Galata separate from Istanbul, despising it as a haven of "infidels"). The nephew of Galata's podestà, Lomellino, along with the sons of surviving Byzantine nobles, were taken as hostages by the sultan (they were assigned to serve in the sultan's palace, with the most attractive sent to Mehmed's personal harem).
In early June 1453, the first Friday prayer was held in the Hagia Sophia in the presence of the sultan and his entourage. A wooden minaret was hastily added to the former cathedral, the cross on its dome was replaced with a crescent, and the mosaics and frescoes inside were whitewashed (except for the four guardian angels under the vaults).Later, under Bayezid II, a second minaret was built, and under Selim II, the remaining two were added. The interior was furnished with a mihrab, minbar, a maksura (a platform for the sultan), and other mosque attributes. Large discs bearing calligraphic inscriptions glorifying the Prophet and the first caliphs were hung on the columns at the gallery level. Similarly, most Byzantine churches and monasteries were converted into mosques and sufi lodge. However, the superstitious Mehmed preserved many "pagan" symbols of the city, such as the equestrian statue of Justinian opposite Hagia Sophia and the columns on the Hippodrome. In contrast, he ordered the Golden Gate, through which Byzantine emperors entered the city (and through which, according to prophecy, Constantine was to return), to be bricked up.According to legend, when the Ottomans stormed Constantinople, an angel saved the last Byzantine emperor, turned him to marble, and hid him in a cave beneath the Golden Gate, where he awaits his time to reclaim the city for Christians. Unlike the Golden Gate, the Charisius Gate, renamed the Edirne Gate by the Turks, became a symbol of Ottoman triumph and the site of annual celebrations commemorating the conquest of Constantinople. Soon, the sultan's spiritual mentor, Sheikh Akşemseddin, announced the discovery of the tomb of Abu Ayyub al-Ansari, the standard-bearer of the Prophet Muhammad, who died during the Arab siege of Constantinople in 674. Over time, on the advice of court astrologers, Mehmed ordered the removal of the giant statue of Justinian from its pedestal, which then lay on the square for a long time until the sultan's heirs melted it down in pieces in a foundry.
The Ottoman authorities sought to quickly restore the economic significance of the conquered city, resettling not only Turks but also peoples of the empire traditionally engaged in trade and crafts. The sultan ordered the repopulation of the depopulated city with Turks from Aksaray, Karaman, and Samsun, Armenians from Bursa, Tokat, Sivas, and Kayseri, Greeks from Sinop, Trabzon, Morea, and the Aegean islands, and Jews from Thessaloniki. Entire quarters in Istanbul were populated by immigrants from cities and regions of Asia Minor, named after their "small homelands" (e.g., Aksaray, Karaman, Çarşamba, and others), as well as Greek and Armenian quarters. By Mehmed's order, settlers were given homes abandoned by Byzantines and Latins, along with various incentives to encourage their engagement in crafts and trade. The development of Istanbul's economy and extensive construction in the city led to further population growth, attracting craftsmen, merchants, sailors, engineers, and officials from across the vast empire. Since non-Muslims (dhimmi) in the Ottoman Empire were barred from bureaucratic or military careers, most engaged in crafts or trade. Other priority measures taken by the sultan to restore Istanbul's vitality included appointing a vizier responsible for maintaining order in the city, gradually recruiting officials to replace the vanished Byzantine administration, restoring city walls, government buildings, private homes, and water supply systems, and concluding agreements with Italian trading cities on new rules for operating in the Ottoman capital (initially, Mehmed II reinstated most of the Genoese privileges in Galata, and later allowed Venetians and other "Franks" to settle in Istanbul).
Mehmed also ordered the Greeks to elect a new Orthodox patriarch, and the monk Gennadius Scholarios, who had escaped enslavement in Edirne and returned to Istanbul, was chosen (after the sultan's approval, the synod merely formally confirmed him). Gennadius II's consecration as patriarch took place in January 1454 in the Church of the Holy Apostles, the second-largest and most significant church in Istanbul, which became the cathedral of the Constantinople Patriarchate (a quarter of early Greek settlers even formed around it). Under the new authorities, the Constantinople patriarch was not only responsible for the conduct of Istanbul's Greeks and other Orthodox Christians but also became the head of the Christian millet of the Ottoman Empire, overseeing Orthodox believers in Asia Minor, Greece, Bulgaria, Romania, Serbia, and Albania (additionally, the patriarchs of Jerusalem, Antioch, and Alexandria were subordinate to him). Istanbul's Christians lived in their own separate quarters and were allowed to retain several churches and monasteries. They were required to wear distinctive clothing and were prohibited from possessing weapons. The Turks imposed special taxes (jizya) on all non-Muslims in the capital.