The decisive encounters between the East and West-- Islam and Christendom--in the fields of war or peace had the most far reaching effects on their destinies. This is one of the most important subjects of Islamic history, indeed perhaps the most important of all. Besides its abundant and eventful episodes, it throws much light on this eternal struggle between the East and the West. As many of these events are scantily dealt with by the Islamic chroniclers, careful reference to Western sources and scholars been made to analyse the subject in detail.