Osman I
Osman I (c. 1258 – c. 1324), also known as Osman Gazi, was the founder of the Ottoman dynasty as the leader of the Kayı tribe of Oghuz Turks, establishing a beylik in Söğüt, northwestern Anatolia, that evolved into the Ottoman Empire through expansion against the weakening Byzantine Empire.[1][2]
Son of Ertuğrul Gazi, Osman assumed leadership around 1281 following the decline of the Seljuk Sultanate of Rûm, declaring independence circa 1299 and initiating ghazi-style raids on Byzantine territories.[3][1]
His key military achievements included the capture of forts such as Karacahisar in 1288 and İnegöl, culminating in the decisive victory at the Battle of Bapheus in 1302, which halted Byzantine counteroffensives and secured Ottoman control over the region.[2][1][3]
Under his rule, the principality expanded to encircle Byzantine holdings like Bursa, which fell shortly after his death in 1326 under his son Orhan, marking the transition from tribal beylik to nascent empire; historical accounts derive primarily from later 15th-century Ottoman chronicles, with contemporary evidence limited, underscoring the challenges in distinguishing core events from subsequent legendary embellishments.[1][3][2]