Title: Why were the Crusades unsuccessful? - Quora
Headings: Why were the Crusades unsuccessful?
Why were the Crusades unsuccessful?
Anonymous

Content: While this was off the back of the Byzantine envoys turning up, no-one seriously thinks that the Pope promoted the crusade for purely selfless reasons to help the Byzantines. At the very least he wanted to re-establish Roman hegemony over the Eastern Orthodox Church, which in 1054 had split from Rome, a schism which remains to this present day. In addition to this it seems that he was keen to increase the power of the papacy, as during this century the investiture controversy had really kicked off (should the king or the church appoint bishops, oddly enough they disagreed on the answer). A crusade would promote loyalty amongst Western Christendom and be a rallying cry. In addition to this was the awkward fact that since the Islamic invasion of the late seventh and early eighth century, the original Christian lands of the Middle East were under Muslim rule and so this needed rectifying. The First Crusade was remarkably successful as they captured Jerusalem and it was returned to Christian control. This remained the case for some time, however over the next few centuries these gains were not only lost but reversed. In 1453 the Ottomans captured Constantinople, a significant Christian city, and swept into Eastern Europe. They remained there until the break-up of the empire after the First World War (1914-1918). So again, short-term, there was some success but long-term it was disastrous.