In 1280, a Turk named Osman became the Bey of Söğüt, Turkey, and over the next 20 years, he took control of neighboring tribes and towns. His son Orhan named the new group the “Osmanlı,” or as we would say now, the Ottomans. In Osman’s time, they were just Turks, and perhaps not even much of a tribe, more like a political block. But any real estate agent will tell you what matters: location. Söğüt was far from the areas where Turks had clashed with Franks during the Crusades; it was in the heart of the old Roman empire, in Bithynia.
Bithynia is a long swath of land along the southern Black Sea coast; it was a kingdom in the Hellenistic period, then a Roman province. Its western edge touches the Bosporus Strait (at Constantinople), and its eastern edge is bounded by the Sakarya River. In the time of Emperor Justinian, they built a massive stone bridge where the military road met the river. The chief city of Bithynia, Nicaea, had just been serving as the seat of the Greek Byzantine government in exile. With the Greeks back in control of nearby Constantinople, Nicaea should have been a secure part of its territory. But Osman’s Turks were attacking many Byzantine towns to their north: Nicaea, Prussa, and the port town of Nicomedia.
The Byzantine Empire was trying to recover its lost footing by crowning father-son pairs as co-Emperors, so that succession was clear and they could send one ruler on military campaign while the other secured the city. Emperor Andronikos II Palaiologos had used marriages, including his own, to bring rival claimants into the family. He had resettled displaced persons from the long Venice-Crete-Constantinople wars around the Meander River (worth mentioning just for its name), and he had hired mercenaries from among the Alans (who were probably part of a Mongolian confederation, therefore loosely allies). Now in 1302, his son Co-Emperor Michael led a large force to confront the Turks on a field between Nicomedia and Nicaea.
The Battle of Bapheus was a simple engagement; the confederated Turks led by Osman overwhelmed the Byzantine army until it fell back to Nicomedia. From that point on, Bithynia was ruled by the Byzantines only from its forts, while the countryside became a no-go zone. When the town of Prussa fell, it became the Turks’ new capital. The name “Prussa” in Greek turned into “Bursa” in Turkish; it was also called “new town” in Turkish. Osman’s son Orhan ruled from Bursa and continued his conquests. In 1337, the port Nicomedia also fell to the Turks. From this point on, Osman’s line grew in power until now we can look back and see Bursa and Söğüt as the origin of the Ottoman Empire.
Also from this point, Muslim history is mostly the story of Ottoman growth. In 1335, still many years before the Black Death broke out in Europe, an early round of the plague carried off the last Ilkhan and his heirs. His territory broke into small fiefdoms and declined in power; Iran was not powerful again until the Safavid Empire in 1501. Everyday life went on as usual, but few Muslims in the 1300s enjoyed the privileges of Empire, as many had done in the past, and many would again in the future.