The Byzantine-Ottoman wars are a series of decisive conflicts between the Ottoman Turks and the Byzantine Greeks that lead to the final destruction of the Byzantine Empire and the rise of the Ottoman Empire.After the loss of Constantinople in 1204, the Byzantine Empire had been left divided and in chaos; taking advantage of the situation the Sultanate of Rum had begun seizing territory in Western Asia Minor until the Nicaean Empire had been able to repulse the Seljuk Turks against the remaining territories still under Greek rule.

Eventually Constantinople had been retaken from the hated Latin Empire in 1261 by the Nicaean Empire.

However the position of the Byzantine Empire in the European continent had remained uncertain due to the presence of the rival kingdoms of the Despotate of Epirus, Serbia and the Second Bulgarian Empire.

This, combined with the reduced power of the Sultanate of Rum (Byzantium's chief rival in Asia) had led to the removal of troops from Asia Minor to maintain Byzantium's grip on Thrace.

However the weakening of the Sultanate of Rum had by no means been a blessing to the Empire as fanatical ghazis have begun setting up their fiefdoms, at the expense of the Byzantine Empire.

While many Turkic Beys participate in the conquest of Byzantine and Seljuk territory, the territories under the control of the Bey Osman I pose the greatest threat to Nicaea and to Constantinople.

By 1299, Osman I feels assured of his position to declare himself Sultan and hereafter his territories become known as the Ottoman Empire.Within 50 years of Osman I's establishment of the Beylik, Byzantine Asia Minor ceases to exist and by circa 1380 Byzantine Thrace is lost to the Ottomans.

By circa 1400, the Byzantine Empire resembles nothing more than a collection of loosely aligned Morean forts and the land immediately around the Capital.

The Crusade of Nicopolis in 1396, Timur's invasion in 1402 and the final Crusade of Varna in 1444 allows a ruined Constantinople to stave off defeat until 1453.

With the conclusion of the war Ottoman supremacy becmes established in the eastern Mediterranean.