Jabarkan Battle dari Pertempuran Bapheus

To counter the threat to Nicomedia, Michael's co-emperor Andronikos II Palaiologos (r. 1282–1328) sent a Byzantine force of some 2,000 men (half of whom were recently hired Alan mercenaries), under the megas hetaireiarches George Mouzalon, to cross over the Bosporus and relieve the city.

At the plain of Bapheus (; an unidentified site, perhaps to the east of Nicomedia but within sight of the city) on 27 July 1302, the Byzantines met a Turkish army of some 5,000 light cavalry under Osman himself, composed of his own troops as well as allies from the Turkish tribes of Paphlagonia and the Maeander River area. The Turkish cavalry charged the Byzantines, whose Alan contingent notably did not participate in the battle. The Turks broke the Byzantine line, forcing Mouzalon to withdraw into Nicomedia under the cover of the Alan force.