By the end of the Byzantine Empire's existence, the old age had weakened both the state and church, making it an easy target for invading forces.

The most notable invaders were the the Turkish-speaking Seljuks, led through a series of battles by Kutalmishouglu Suleiman, who supported different usurpers against the Byzantine emperor. The expansion of the Seljuks was so successful that when Suleiman died, he had put all of Bithynia under his control as well as several important harbor towns along the shores on the Asian side of Bosphorus. With that accomplishment, he had managed to separate the Byzantines living in Anatolia from their emperor in Constantinople. This immediately weakened the unity of the Byzantine Empire.

When another invading Muslim army took control of what is now Syria, Israel, and Northern Africa, the dismembered Byzantine Empire lost significant portions of land, but that allowed it to grow into a smaller and stronger unity. It took a lot of power struggles and battles on many fronts for the empire to recapture some of the lands, but gradually the Byzantine Empire lost all influence in Anatolia. By the end of the 11th century, the Hellenic culture and Greek language were replaced by Islam and Turkish.

Of all the conflicts that brought this state of affairs into being, few were as instrumental as the Battle of Kapetron, the culmination of one of the first major Seljuk raids into Byzantine territory. It represented not just a clash of ethnicities, cultures, and religions, but also a harbinger of a changing of the guard, and one that would shape geopolitics in the region for the next several centuries.