On 28 May 1453 the walls of Constantinople were finally breached by gunpowder weapons, allowing the Ottoman Turks entry into the city. Streaming through the breaches, the elite Janissaries quickly opened the gates, then they and other Ottoman soldiers spread through the large city. The Janissaries proved extremely respectful of the Constantinopolitans. Disciplined and well trained, they did not rape, ravage, or pillage, nor kill anyone unarmed or begging for their lives. The same could not be said for the irregular forces, who were given three days of pillage, the period allowed by the Qur'an according to Ottoman religious leaders. Yet even then Mehmed had set limits: Hagia Sophia would be his, the world's greatest Christian church becoming a monument to an epoch-making Islamic victory. The sultan meant it, too. He personally cut off the head of an irregular soldier whom he found attacking the icons in the Hagia Sophia with a sword. Neither was the Church of the Holy Apostles to be violated, remaining a place of worship (albeit the only one) for the Christians who would continue to live in the city. As Runciman notes, ‘the Greeks, as the second people in his Empire, could keep the second great church’.

The reason for Mehmed's restrictions was simple. Long before his attack on Constantinople, he had decided to make the city his imperial capital. Conquerors are different from invaders.