Why did Osman Bey pledge allegiance to Yaqoob Bey, the Garmian chief..?? Othman Bey therefore pledged allegiance to Yaqoob Bey, perhaps Othman Bey had already received information about the arrival of the Mongols and had to gather tribes to fight the Mongols, and now the tribes are with Yaqoob Bey, so Othman is without an army. Yaqub will use Bay to gather. This is my opinion, the rest of you must give your opinion.