Osman I

Osman I declared independence from the Seljuk Sultanate of Rum, establishing his own beylik (principality) in northwestern Anatolia. This act is traditionally considered the founding of the Ottoman state, which would later grow into a vast empire.

Osman I led his forces to victory against a Byzantine army at Bapheus near Nicomedia. This battle established Osman's reputation as a ghazi warrior and marked the beginning of Ottoman expansion into Byzantine territory in northwestern Anatolia.

Osman I formed a temporary alliance with the Byzantine emperor Andronikos II against the Catalan Company. This pragmatic relationship allowed Osman to gain resources and recognition while expanding his territory.

Osman I initiated the siege of the Byzantine city of Bursa, though it was captured by his son Orhan after Osman's death. The conquest of Bursa provided the Ottomans with their first major urban center and capital.