Osman I Founds the Ottoman Beylik
A frontier chieftain stops paying tribute to the Mongols and starts a state that will outlast every rival
Quick facts
- Founder
- Osman I (Osman Gazi), c. 1258-c. 1323
- Founding act
- c. 1299, ends tribute to the Mongol Ilkhanate
- Region
- Bithynia, northwestern Anatolia
- Key early victory
- Battle of Bapheus, 1302, over Byzantine forces
What happened
Osman I, also called Osman Gazi, led a small beylik in Bithynia, on the frontier of northwestern Anatolia just south of Byzantine Constantinople, one of many Turkish principalities that had splintered out of the collapsing Sultanate of Rum. Around 1299 Osman stopped paying tribute to the Mongol Ilkhanate that nominally still claimed authority over Anatolia's beyliks, an act treated as the effective founding of an independent Ottoman state, and pressed his forces against Byzantine territory, laying siege to Nicaea that same year, though the siege itself failed. In 1302 his forces defeated a Byzantine army at the Battle of Bapheus, after which, in the words of one modern account, Byzantine hegemony in Bithynia further evaporated, and Osman went on to besiege the city of Prusa starting in 1308.
Why it matters
Of the dozen or more Turkish beyliks competing across post-Seljuk Anatolia, Osman's frontier principality was the one that grew into the Ottoman Empire, which would rule from the Balkans to the Persian Gulf for six centuries and give Turkey its dynasty, its later capital at Constantinople, and much of its national self-image. Everything the Ottoman Empire timeline covers in detail, from Mehmed II's conquest of Constantinople to Suleiman's Vienna campaigns, starts here, with a chieftain who quit paying tribute to the Mongols.
How we know
Osman I's early campaigns against Byzantine Bithynia, including the 1299 siege of Nicaea and the 1302 Battle of Bapheus, are recorded in both early Ottoman chronicles composed within a century of his death and in Byzantine historical accounts of the same border conflicts.
Sources
- World History Encyclopedia. Osman I · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- World History Encyclopedia. Ottoman Empire · Reputable sourceworldhistory.org · The domain "worldhistory.org" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
See something wrong? . Corrections with a source get fixed fastest.
Related timelines
- The Ottoman Empire → · Osman's beylik is the direct starting point of the Ottoman Empire; see that timeline for the empire's rise, peak, and six centuries of rule.