It is tempting to associate Christian holy war (epitomized by the crusades) with the jihad, but Christian traditions of positive force war were established in the fourth and fifth centuries and the jihad was born independently in the seventh. The only link between them seems to have been provided by the human condition, since it is hard to think of a religion, including Buddhism, which has not developed its own version of holy war. It is also striking how often warfare of this type sooner or later turns in on itself as its protagonists come to believe that it cannot be successful if the society which has generated it remains impure and defiled. Reverses in crusading led to demands for the reform of Christendom and to the preaching of holy war against the Church's political enemies and heretics. Likewise, summons to jihad have often been accompanied by calls for moral rearmament and the extirpation of heresy at home.

This is the best introduction to the theory and practice of jihad that has yet appeared, and should be read by everyone looking beyond Islam itself for the seeds of its holy-war doctrine. It is exceptionally well written, clear, decisive in its opinions, but fair to those held by others. Each chapter ends with a useful short bibliography. After introducing his readers to the concept and drawing attention to historiography and to modern debates, Professor Bonner devotes seven chapters to the early centuries. The apparent imbalance in the book is justified because it enables Bonner to put before the reader the various elements in what is a complex and many-stranded group of ideas, including the relationship of the believer towards God, the concepts of martyrdom and dar al-Islam, the importance of events on Islamic frontiers against the Byzantines, the Turks, and in Spain, and the emergence of scholars of war who played a crucial role in the definition of jihad. Bonner makes the point that although notions of jihad existed from the birth of Islam, the doctrine truly evolved only toward the end of the eighth century. In the course of two chapters covering the development of the concept in the great Muslim empires and in resistance to European imperialism, he touches on the crusades.

Although Bonner underestimates the importance of embryonic rules of war, by which both parties abided from the start, he is enlightening on what scholarly fighters and ghazi sultans contributed to resistance against the crusaders. It becomes clear how much the thinking of Muslim political and intellectual anti-crusading leaders owed to the earlier developments. This is true even of radicals like Ibn Taymiyya—so significant an influence on modern Islamism—who wanted the jihad to turn inwards, to purify the dar al-Islam before it could over-run the rest of the world. Bonner's last chapter contains a brilliant summary of the ideas of the Egyptian thinker Sayyid Qutb (d. 1966), which should be essential reading for modern Western politicians.