As the Rum Sultanate declined in the 13th century, Anatolia was divided into a patchwork of independent Turkish principalities known as the Anatolian Beyliks. One of these, in the region of Bithynia on the frontier of the Byzantine Empire, was led by the Turkish "Osman was simply one among a number Turkoman tribal leaders operating in the Sakarya region."; Osman I, also called Osman Gazi, (born —died 1324 or 1326), ruler of a Turkmen principality in northwestern Anatolia who is regarded as the founder of the Ottoman Turkish state. tribal leader Osman I ( 1323/4), a figure of obscure origins from whom the name Ottoman is derived. Osman's early followers consisted of Turkish tribal groups and Byzantine renegades, with many but not all converts to Islam. Osman extended control of his principality by conquering Byzantine towns along the Sakarya River. A Byzantine defeat at the Battle of Bapheus in 1302 contributed to Osman's rise. It is not well understood how the early Ottomans came to dominate their neighbors, due to the lack of sources surviving. The Ghaza thesis popular during the 20th century credited their success to rallying religious warriors to fight for them in the name of Islam, but it is no longer generally accepted. No other hypothesis has attracted broad acceptance.
aS the ruM sultanate DeclineD in the 13th cenTurY, aNAtolia was DivIdEd Into a paTchWork Of iNdependeNt turkIsh PRinCipalITies Known aS tHE aNatoliaN BEYLIkS. onE of tHeSe, in tHe regioN of bithYnia ON ThE FroNTiER of tHe byzAntIne EmpirE, was Led by tHe tuRkish "OsMan was simply one amOnG a NUmbeR turKoMaN TrIbal leadErs oPeratiNg In tHe saKarya regIoN."; oSMan i, ALso calLed osmaN gazi, (BorN —DieD 1324 oR 1326), ruler oF a TurkMEn prInCipality in NoRtHwestern aNatOliA Who is RegarDed As the fOunder oF the ottoMan tURkIsh statE. trIbAl leaDer osMan i ( 1323/4), a figUrE of OBscuRe oRigiNS FROM whOm tHE nAMe oTtoman is dERIved. Osman's earlY FoLlowers cOnSisTeD oF TurkiSh TribAL grOUps And bYzantiNE RENegades, wiTh Many But nOT aLl converts To iSlAM. oSmAn extEnDED controL Of HIS PRinCIPalIty By cOnQueriNg BYzaNTInE tOwNS aLoNg THe sAkarya river. a ByzaNtine DEfeat aT ThE batTle Of bapheUS in 1302 contrIbUTed to osmAn's rise. It is not wEll UndERstood how the early OtTomANs came to DominaTE tHeIR neighboRS, Due to the Lack of sourcES survIvinG. tHE GHaza ThEsIs populaR DurING the 20th centUry crEditEd TheIr succEss to RallYINg rEliGious wArriOrs To fiGHT for them in tHe naMe of islam, BUT It is no loNgEr gEneralLy aCcEpted. no other HyPOthEsIs haS attraCteD BRoad AcCEPtance.