One reason, or trigger for Pope Urban calling the crusade would have been Alexius’ request for his help. Alexius asked for Pope Urban’s aid in helping him to fight the Turks; this is because they were closing in and starting to invade Constantinople, which was the main frontier between the Christian and Islamic worlds. Emperor Alexius felt threatened by the Turks, and knew that Pope Urban in him being the head of the Church (the most powerful and influential part of society) would have enough superiority, and power to fight the Turks and their leader Malik Shah. Although Malik Shah died soon after; they both knew that they would need an army of some sort to protect their land. Therefore Pope Urban knew from Alexius’ request that he would have to be prepared for a long fight ahead, to ensure the safety of the Christian religion, and Holy lands.
Secondly, Pope Urban may have called for a Crusade for his own personal gain. Pope Urban would have realized that if he didn’t take action against the Muslims then he would loose power to them, as well as land and security. Therefore, Urban would only become more powerful if he called for a Crusade. This is because if he defeated the Muslims they would have to respect him more, and he would be seen as more powerful in everyone’s eyes as he led a Crusade. Urban probably also realized that Crusades sometimes resulted in more riches and resources, which he would have kept for himself making him richer and higher up in the Feudal system.
Another reason could be that the papacy didn’t have a say in political situations, Urban may have wanted that to change. Therefore calling upon knights and nobles, and having them respond to you was one way of slowly gaining power over them as well. Resulting in more power not just in religion, but also in the Investiture Contest. Urban would have wanted more say in what Bishops were chosen, and more power on the