On the 27th November 1095, Pope Urban II launched the First Crusade with an impassioned speech at the Council of Clermont. The Byzantine Emperor Alexios I Komnenos had appealed to the Pope for support against invasion by the Seljuk Turks, and many historians argue that Urban II took advantage of the situation as a way to reunite Christendom under the papacy.
By the 11th Century, Christianity had secured a stable base across most of Europe. However the Byzantine Empire was on the very periphery and faced continuous threats from Muslim conquests. The city of Jerusalem had been in Muslim hands since 638, but ongoing wars between different Arab dynasties had resulted in it being captured by the Seljuks in 1076. When their army began threatening to attack Constantinople, Alexios appealed to the Pope for assistance.
There is no record of how many people responded to the Pope’s call, but estimates suggest anywhere between 60,000 and 100,000 of which a large number were ordinary peasants. Exactly why so many people chose to “take the cross” is also a question subject to fierce debate. Certainly some nobles went in the hope of seizing riches along the way, but a large number of crusaders almost certainly did so out of piety.
Although Pope Urban had intended the Crusade to depart on the 15th August 1096, large numbers of peasants and low-ranking knights set off earlier on what became known as the People’s Crusade. Poorly disciplined and with little to no military training, these Crusaders killed thousands of Jews in the pogroms of 1096 before even leaving Europe.