The interest of Michael VIII in the western territories of the Empire, the neglect of the system of defence on its eastern borders and the general penury of the state, all of which became strikingly manifest during the years of Andronikos II, favoured the expansion of the Turks in Asia Minor. By 1300, the entire Byzantine hinterland of Asia Minor had submitted to the Turks, who established there a number of small sovereign states. Only a few cities, such as Nicaea, Nikomedeia, Prousa, Sardis, Philadelphia, Magnesia, Herakleia Pontike, Phokaia and Smyrna still remained Byantine.

Andronikos II turned his concern towards the re-organisation of defence in the region. In 1293 he appointed the able general, Alexios Philanthropenos, commander of the army of the East, but the latter rose in revolt against the emperor, and for that act was blinded (1295). Philanthropenos was succeeded in 1297 by John Tarchaneiotes who took measures to bring about reforms in the region. These measures, however, were fiercely opposed by all the great landowners and the clergy of the Eastern provinces and, in 1300, he was forced to withdraw.

The defeat of the Byzantines by Turkish troops at the battle of Bapheus in 1302 placed Andronikos II in an extremely difficult position. Believing that the mercenaries of the Catalan Grand Company would extricate him from this difficulty, he hired the Company in 1304 to assist him in halting the Turkish invasion. But the new problems created by the Catalans for the Byzantine state and the civil war that broke out shortly afterwards between Andronikos II and his grandson Andronikos III, allowed the invaders - mainly Ottoman Turks - to spread in Asia Minor. In 1326 they seized Prousa, which became the capital of their state.