Mehmed II came to the throne for good in 1451, at nineteen, and within two years did what Muslim armies had attempted on and off for eight centuries. The conquest of Constantinople in 1453 earned him the title Fatih, "the Conqueror". The siege itself, with its giant cannon and its ships dragged overland into the Golden Horn, belongs to the story of Byzantium. This level asks a different question: what did Mehmed do with the city, and how did the conquest change what the Ottoman state believed itself to be?

Rebuilding a capital

The Constantinople Mehmed entered was half empty. Its population had been shrinking for two centuries, and the sack that followed the conquest killed or enslaved many of those who remained. Mehmed set out to refill it. He used forced resettlement, known as sürgün, moving Muslim, Christian and Jewish families from across the empire into the city, while also inviting merchants and craftsmen to come of their own accord. Officially the Ottomans long called it Kostantiniyye, a form of its old name, while Istanbul, probably from a Greek phrase meaning "to the city," was the everyday name.

Mehmed built for permanence. He converted the great church of Hagia Sophia into a mosque, raised a vast new mosque complex, and began the palace later known as Topkapı on the old acropolis above the Bosphorus. To lead the city's Orthodox Christians, Mehmed installed the scholar Gennadios Scholarios as patriarch in 1454, giving the church a recognized place under Muslim rule. Governing through existing religious leaders became a lasting Ottoman habit.

Heir to Rome

Mehmed saw himself as more than a frontier sultan. He took the title Kayser-i Rum, Caesar of Rome, and gathered Greek and Italian scholars at his court. In his vision the Ottoman ruler combined three inheritances: Turkic and Mongol traditions of steppe kingship, the Islamic duty to protect and extend the faith, and the universal claims of the Roman emperors. That blend shaped Ottoman ideas of rule for centuries.

He also tightened the dynasty's grip on power. The Interregnum had shown how dangerous rival brothers could be. A law code attributed to Mehmed allowed a new sultan to execute his brothers, justified as necessary to keep the order of the world. He kept expanding as well, absorbing Serbia, the Morea in southern Greece, the Greek empire of Trebizond on the Black Sea and Bosnia, though he failed to take Belgrade in 1456 and Rhodes in 1480. He died in 1481.

Selim and the turn east

Mehmed's son Bayezid II, who ruled from 1481 to 1512, consolidated more than he conquered. His son Selim I, called Yavuz, "the Stern" or "the Grim," forced him from the throne in 1512 and turned the empire's attention east and south. The main threat there was the Safavid dynasty of Iran. Its founder, Shah Ismail, had made Twelver Shi'ism the state religion and drew devoted followers from the Turkmen tribes of Ottoman Anatolia. At Chaldiran in 1514, Selim's army, with its cannon and Janissary musketeers, defeated Shah Ismail's cavalry. The long Ottoman and Safavid rivalry that followed helped harden a line between a mostly Sunni west and a Shi'i Iran.

Selim then attacked the Mamluk sultanate, which ruled Egypt and Syria. Victories at Marj Dabiq in 1516 and Ridaniya in 1517 brought Syria, Egypt and the Hejaz under Ottoman rule. With Mecca and Medina came the title Servant of the Two Holy Sanctuaries, marking the sultan as the leading ruler of the Sunni world. A later story claimed that the last Abbasid caliph, living in Cairo under the Mamluks, formally handed the caliphate to Selim. Historians doubt the tale, which appears in sources written long after the event, at a time when sultans had reasons to stress their claim to be caliph.

Worked example: judging the law of fratricide

Fratricide strikes modern readers as monstrous, and it was: Mehmed III, on taking the throne in 1595, had nineteen of his brothers killed. But a historian's task is to understand a practice before judging it, and then to judge it honestly. Start with the problem it addressed. The Ottomans had no fixed rule that the eldest son inherits; any son of a sultan could claim the throne, and each had backers among soldiers and officials who hoped to rise with him. The Interregnum after 1402 showed that rival claimants could tear the state apart for a decade.

Now weigh the solution. Fratricide made a succession final, so that losers could not become rallying points for rebellion or tools of foreign enemies. It did not end conflict, since princes still fought before their father died, as Selim fought his brothers. And its moral cost was enormous: boys were killed for what they might do, not for anything they had done. From the early seventeenth century the dynasty moved away from the practice, confining princes in the palace instead and passing the throne to the eldest male of the family. The case shows a pattern worth remembering: a state may solve a real problem by treating some people merely as threats to remove, and the moral question does not vanish because the political logic is clear.