The town of Osmaneli was first occupied and turkified by the Seljukians, who were on route to conquering the town of Iznik. Osmaneli, then known by its former name "Lefke", and Iznik then joined the Seljukians and founded the Anatolian Seljuk State in 1075. During the crusades no one tried to enter Osmaneli as Turkish warriors were living there, leading the town to be uninterruptedly occupied by Turks.