There have been many wars started for religious reasons. The most famous of these are the Crusades that took place from 1096 to 1193. The European Christians sought to recapture the Holy Land, the city of Jerusalem, from the Moslems and Turks (aho also claimed it as a holy site). The irony to this is that these so called Christians slaughtered Jews and other Christians on their way to Jerusalem and in the city itself. If you want to read a fascinating book about this, chack out "The Crusades Through Arab Eyes" by Amin Maalouf or read James Michiner's fictional masterpiece "The Source."