A Catechism of Defending The Crusades and Other Aspects of the Medieval World Part III

Objection 9: Why did the Crusades not start until four hundred years after the rise of Islam?
 Response: In reply to the first part of this objection, especially in relation to the Latin Christians, it has already been answered by the previous statement. In other words, the violence of the Seljuk Turks towards the Latin Christians was particularly what brought on the Crusades. However, in relation to the Eastern Christians it should be noted that the west was still recovering from the barbarian raids in the north that had helped bring an end to the Roman Empire.
 Further Sources: The Usborne Time Traveler Book of Knights and Castles by Judy Hindley, Rome at War: A.D. 293-696 by Michael Whitby.   

 Objection 10: Did the medieval church first try to evangelize the Muslims before initiating The Crusades?
 Response: The medieval Latin Church was quite evangelistic throughout much of it's history. Even when paganism had essentially taken over most of Europe in the early middle ages it was monks from both Rome and Greece that evangelized much of Europe back to Christianity. Frequently, open air preaching was a common form of evangelism among friars in the Medieval Eras for example.
 The fact that the Roman Church had to first evangelize the Celts, the Saxons, and the other people groups of Western Europe partly explains the fact that the Roman Christians were tied up with events in Medieval Europe. With such business in the west this may have contributed such success to Islam's successful rise to conquest in the east. If anyone is to blamed for a lack of evangelism towards the Muslims, it would be the Greek Christians, whom more commonly submitted to the Muslims than had the Latin Christians. Aurelius and Natalia were two Christians put to death in A.D. 852 for not submitting to Islam. A Christian monk by the name of George, spoke against the prophet Muhammad, and was also put to death with Aurelius and Natalia.
 Saying that the crusades were morally wrong because the Muslims should have been evangelized instead, is a weak argument primarily because even if the medieval church had not evangelized the Muslims, it would not have made the crusades morally unjust. For example, America was right to trample the Nazis in World War II, a war that President Eisenhower had called a ''holy war. '' World War II would have been morally just whether or not the Nazis had been evangelized.
 Further Sources:  The Medieval World: The Illustrated History of the Middle Ages by Anita Baker, Saint Francis of Assisi and the Conversion of the Muslims by Frank W. Rega.

 Objection 11: The Scriptures should not have been used to justify The Crusades.
 Response: The Holy Scriptures teach a time and place for capital punishment and just war
{ Ecclesiastes 3: 8. , Romans 13 }. Still, for the record, the medieval church rarely, if ever, actually used the book of Joshua to defend the crusades. In fact, the books of Maccabees were used more commonly to defend the crusades because the Hebrews in first and second Maccabees are fighting to take Jerusalem back from the Greeks. King and Saint Louis IX, did justify the Crusades in a particular letter by using the story of Joshua and the Hebrews. But again, Maccabees was more commonly used for the justification of the Crusades.
 It should also be noted, and as talked about in a previous post, contrary to myth, Pope Urban II did not tell the crusaders to kill all those that inhabited Palestine. The pope's command at Clermont France in July of 1095, was that the Christians should recapture the Holy Land.  The pope only wished the infidels to be slain if they did not forsake the holy places. Thus, the pope did not preach
some false gospel, or in any way claim the same authority or power that God had given particularly to the Hebrews in Joshua when they killed all in their path. 

 Objection 12: Unlike the Book of Joshua, the crusades were not called by a divine act of God, and therefore they had no right forcing the Muslims into their faith. Some of this was already addressed in the previous post. Further, nothing in Scripture claims for a war to be considered holy or proclaimed holy that God must first initiate it by an outward act of His divine will. Governments according to Scripture have the right to carry the sword to protect their peoples. As was explained earlier, it was the Muslims  Seljuk Turks that had made their wars with the Western Europeans and started the whole history of religious conflicts between Christians and Muslims to began with.
 Further Sources to the above answers: The Politically Incorrect Guide to Islam and the Crusades by Robert Spencer.