Final answer:
The Byzantine emperor requested help to defend against the Seljuk Turks, leading to the Crusades initiated by Pope Urban II.
Step-by-step explanation:
The Byzantine emperor reached out for assistance against the Seljuk Turks. The Seljuks were a Turkic power that challenged Byzantium's territories, especially in Asia Minor, throughout the eleventh century. An emperor, Alexios I, famously called upon the European powers for assistance, hoping for a mercenary force against the Seljuks. However, Pope Urban II instead ignited the crusading movement, framing it as a religious conflict. This call for help inadvertently led to the advent of the Crusades, a series of religious and military expeditions.