The Ottomans crossed into Europe in 1354, when an earthquake collapsed the walls of Gallipoli on the European shore of the Dardanelles and Suleiman, son of Sultan Orhan, took the city. From there the advance into Thrace was rapid, broken only briefly by the bizarre kidnapping of Suleiman's young brother Halil between 1357 and 1359. Once Halil was rescued, the push north resumed. Demotika, the modern Greek town of Didymoteicho, fell in 1360 or 1361. Filibe, Bulgarian Plovdiv, fell in 1363. Even when Byzantine forces under the Savoyard Crusade briefly recaptured Gallipoli in 1366, they could not reverse the broader pattern. Bands of ghazi and akinji warriors crossed from Anatolia in growing numbers, settled the Thracian plain, raided the Rhodope Mountains in the west and the Bulgarian principalities in the north. By the time anyone in Constantinople noticed how thoroughly the map had changed, Adrianople was nearly encircled.

The fall of Adrianople is one of those events that historians cannot quite pin down. Ottoman sources, written long after the events they describe, place it between 1361 and 1363, citing a solar eclipse in the year of the conquest. Later Turkish chroniclers describe the Byzantine governor of the city, the tekfur, defeated at a battle at Sazlidere southeast of the walls, then fleeing secretly by boat. According to those accounts, the inhabitants surrendered in July 1362 in exchange for permission to keep living in the city as before. But the Greek scholar Elisabeth Zachariadou re-examined Byzantine sources in the 1980s, including that Christmas 1366 poem to John V Palaiologos, and built a case that the city remained Byzantine well past the Ottoman dating. Most modern scholars now accept 1369. They also suspect the conquerors may have been not Ottoman troops at all but one of the many independent akinji warbands operating in Thrace, only later folded into Ottoman official memory.

Whoever took the city, the Greeks and other Christians who lived in Adrianople did not flee en masse. They could not have. The city held tens of thousands of people, many of whose families had lived there for generations, sometimes since Roman times when Hadrian had founded the city and given it his name. The terms of surrender, in the Ottoman version of events, allowed the inhabitants to remain and continue their lives as before. In practice this meant becoming dhimmi, the protected non-Muslim subjects of an Islamic state, paying the special tax called jizya in exchange for religious freedom and a degree of communal self-governance. Some converted. Some emigrated to other Byzantine cities. Most stayed. They went on speaking Greek and Bulgarian and the various Thracian dialects, going to their churches, marrying their children, burying their dead. The empire above them changed. Their daily lives, after the first traumatic months, did not entirely change with it.

The city was renamed Edirne, a Turkish reshaping of Hadrianopolis, and continued for some time to be administered by Lala Shahin Pasha, the general usually credited with its capture. Sultan Murad I held court mostly at the old capital of Bursa, in Asia, and only entered Edirne in the winter of 1376-77, after Emperor Andronikos IV Palaiologos ceded Gallipoli to him in exchange for help in a Byzantine dynastic civil war. Even then, Edirne did not immediately become the formal Ottoman capital. The court continued to circulate between Bursa, Demotika, and Edirne for decades. But Edirne was the center from which the Ottomans now ran their Balkan campaigns. When the dynasty was nearly destroyed at the Battle of Ankara in 1402 and a contender named Suleyman Celebi tried to hold the fragments of his father's empire together, he moved the state treasury to Edirne. The city was now indispensable.

From its capture in the late 1360s until the Ottoman conquest of Constantinople in 1453, Edirne functioned as the principal seat of Ottoman power. From its palaces Mehmed II planned the siege that would finally end the Roman Empire. The Selimiye Mosque, which would become the masterpiece of the great architect Sinan, would rise here in the 1570s, its enormous dome answering the Hagia Sophia from across the Thracian plain. To stand in modern Edirne, in Turkish Thrace just over the border from Greece and Bulgaria, is to stand in the place from which an empire built itself before it ever touched Constantinople. The Greek city is gone. The Greek inhabitants and their descendants moved or assimilated or died in the various traumas of the centuries that followed. Their footprint, in street names and church foundations and the layout of certain quarters, remains.