However, the Church did not 'con' the warriors into going on crusade. The warriors were already convinced that God approved of their fighting, and that their warrior skills were more valuable to God than the clergy's praying. The warriors took up the concept of the crusade with enthusiasm because it fitted their own ideas about what fighting was for. The warriors' belief in fighting for God is made clear in medieval epic poetry such as The Song of Roland. By the fourteenth century the crusade had become an essential part of every noble knight's career. It was still an act of faith, but for the noble knights seeking one's own honour went hand-in-hand with seeking God's honour.
The Crusades were equally a result of economic circumstances. Many participants were lured by the fabulous riches of the East; a campaign abroad appealed as a mean of escaping from the pressures of feudal society, in which the younger sons in a family often lacked economic opportunities. On a larger scale, the major European powers and the rising Italian cities (Genoa, Pisa, and Venice) saw the Crusades as a mean of establishing and extending trade routes. Venice in particular assisted the Crusading effort in return for 1/3 of all wealth captured and the promise of free trade markets in the East. Alternatively, some Christians went on Crusades because they wanted to go to heaven or wanted to shorten their time in Purgatory. They also went to be forgiven. Some people went on Crusades because they knew that if they killed a Muslim they would be allowed to take all his belongings, granting them food and money.
It has been argued, that in many cases individual crusaders had no choice in whether they went on crusade or not, because they accompanied their lord or employer. Where they did have a choice, the sources indicate that they went on crusade to fight for God - hoping for the reward of salvation in the next life and booty in this - and to seek glory and honour. Whilst others were forced to go on Crusade by the Church because they had committed a crime or sin. For example, from an English trial in 1291 said, “You have been found guilty of hitting a priest with your sword. For this outrage you must join a crusade or pay a suitable soldier to go instead.” However, this had a relatively small scale impact in attracting people to the Crusades, and it was mainly religious fervour and the potential to gain prestige and wealth that attracted so many Christians.
Gesta Francorum trans. Rosalind Hill
Marcus Bull, Knightly Piety and the Lay Response to the First Crusade: the Limousin and Gascony, c. 970-c. 1130
Jonathan Riley-Smith, The First Crusade and the Idea of Crusading
Fulcher of Chartres, A History of the Expedition to Jerusalem