The fall of Nicaea to the Ottoman Turks was a significant event during the early phase of Ottoman expansion in Anatolia. Nicaea, located in present-day Turkey, held a strategic position and historical importance as one of the last bastions of Byzantine control in the region. The siege, which lasted for several months, showcased the military prowess and determination of the Ottoman forces under the command of Orhan I, the son of Osman I, the founder of the Ottoman dynasty. The city's defenses were robust, but the Ottomans used a combination of military tactics and siege engineering to breach its walls.

The defenders of Nicaea struggled against the larger and better-coordinated Ottoman army. Despite their efforts, including the deployment of mercenaries and local militias, the city ultimately succumbed to siege warfare and bombardment. After the fall, the Ottomans were able to establish a more firm grip over Asia Minor, which had a lasting impact on the region's political and cultural landscape. The capture of Nicaea additionally enabled the Ottomans to cut off the Byzantine Empire's access to a vital city and furthered their ambitions into Europe.

The consequences of the siege extended beyond warfare. Following the capture, Nicaea underwent significant changes in governance and culture as it became integrated into the growing Ottoman Empire. This marked a key moment in the shift of power from Byzantium to the Ottomans in the region, setting the stage for future conflicts and the eventual conquest of Constantinople several decades later. The melding of different cultural influences in the city thereafter played a role in shaping Ottoman identity and administration.