However, towards the end of his reign Manuel's achievements in the east were compromised by a serious defeat at Myriokephalon, which in large part resulted from his arrogance in attacking a well-defended Seljuk position.
I slutningen af hans regeringstid blev Manuels sejre i øst bragt i fare af et alvorligt nederlag i Slaget ved Myriokephalon, som i høj grad skyldtes hans overmod ved at angribe en velforsvaret Seljukisk stilling.