Orhan I in the context of Ottoman army in the 15th–19th centuries

The Ottoman army was the military structure established by Mehmed II (r. 1451–1481) during his reorganization of the Ottoman state and its military. It resulted from a major reorganization of the standing army dating from the time of Sultan Orhan (r. 1323/4–1362), which had centred on janissaries who were paid by salary rather than rewarded with booty or fiefs. The army built by Orhan had operated during the period of the rise of the Ottoman Empire (1299 to 1453).

The organization introduced by Mehmed II was twofold, central (Ottoman Turkish: Kapıkulu, the household division) and peripheral (Ottoman Turkish: Eyalet, province-level). Sultan Mahmud II forced this army to disband on 15 June 1826 in what is known as Auspicious Incident, which followed a century-long reform effort.

The Battle of Pelekanon, also known by its Latinised form Battle of Pelecanum, occurred on June 10–11, 1329 between an expeditionary force by the Byzantines led by Andronikos IIl and an Ottoman army led by Orhan I. The Byzantine army was defeated, with no further attempt made at relieving the cities in Anatolia under Ottoman siege.