Fall of Philadelphia

The Fall of Philadelphia marked the fall of Philadelphia, the last independent Christian Greek settlement in western Asia Minor, to the Muslim Turks of the Ottoman Sultanate. Ironically, the besieging army included a contingent from the Byzantine Empire, which by then was a vassal of the Ottomans.
Prior to its fall, the city had evaded the fate of her neighbours by paying tribute to the numerous fanatical ghazis, whose bands robbed and pillaged any who did not pay protection money ("jizya"), although the city was not officially under Islamic law. In theory, the city was under the Byzantine Empire, but cut off by a sea of hostile land ensured that in reality the city remained independent.
In 1378 Manuel II Palaiologos promised to hand over the city of Philadelphia to the Turks in return for the Ottoman sultan's aid in a disastrous Byzantine civil war. However, Manuel seems to have retracted his promise, since it was not until 1390 that Bayezid summoned the two leaders of the civil war, John VII and Manuel II, and ordered them to accompany the besieging force. The city was taken by the Turks that year.