http://www.credo.ndirect.co.uk/crusades3.html
The Crusades failed in three respects. The Holy Land was not won. The advance of Islam was not permanently checked. The schism between the East and the West was not healed. They were the primary objects of the Crusades.Whatever the official objectives and motivation for the Crusades, the reality was that the crusading armies were a disgrace to the name of Christ. Personal gain in wealth and power became a far more real motive for many of the leaders. The "soldiers of the cross" were savage, cruel and brutal in many cases. They looted and vandalised as they went through both "Christian" and Muslim territory. They fought among themselves more effectively than against the Muslim foe.
At the beginning of the Crusading era, Pope Urban II offered indulgence (forgiveness from sins) for those who took the Cross. Later this was extended to those fighting Christian Heretics in Europe. The whole system of indulgences which developed from this brought about a wholly wrong attitude to sin and repentence. People believed that they could earn the right to sin, or gain forgiveness through works. Eventually, when Popes began to sell indulgences for money, the voices of Luther and others were finally raised in protest.
The ordinary folk who followed the Cross were often men who had previously not been more than a few miles from their own farm or village. Now these same people were experiencing a great mixture of cultures even within their own armies. People were exposed to the cultures of many different countries and to the cultural heritage of times past. They saw evidence of art and architecture from classical times and many were exposed to the very different forms of art to be found in the Muslim world.
It is arguable that literature was deeply enriched by these experiences and also that a thirst for knowledge was engendered even in many who were otherwise illiterate. Much of thre Arthurian Literature was collected or written at this time to encourage the concept of chivalry.
It is arguable that the contact of the Crusaders with other contemporary and ancient cultures encouraged, if not engendered, the Renaissance which, in turn, contributed to the Reformation.
Kevin Brown, Pastor of The Downs Baptist Church, Hackney in East London has written to me at length on this subject and I quote him:
You are right to point out that the idea of Holy War was not initially a Christian concept. Indeed, I only hope you will add that it remains a wholly unChristian concept.I confess that the only Holy War that my Bible refers to is the one described in Ephesians 6:
10 Finally, be strong in the Lord and in his mighty power. 11Put on the full armor of God so that you can take your stand against the devil's schemes. 12For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms. 13Therefore put on the full armor of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. 14Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, 15and with your feet fitted with the readiness that comes from the gospel of peace. 16In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one. 17Take the helmet of salvation and the sword of the Spirit, which is the word of God. 18And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints.Argument about whether Christians should fight in wars at all can be left for other times and other articles. Neither is this the place to debate whether there is such a thing as a "just war". What seems clear to me, however, is that Kevin is right. The only Holy War is that which is fought in the heavenlies, that which John Bunyan refers to as the Battle for Mans Soul. (The Holy War - John Bunyan)