We watch with amazement the Muslim Jihadists of our time, moving from one killing field to another, mobilized, physically and spiritually for the cause of Islam, and risking their lives to accomplish a goal that usually escapes us.

It turns out this practice took root since the inception of Islam, and that its miraculous expansion worldwide was due to a great extent to the masses of volunteers who sprang out of Arabia, heading westward until North Africa and the Atlantic, and on the other hand, to the Iberian Peninsula, and on that side of the globe, they conquered the Middle East, Asia Minor, and Central Asia in a sweep the world has known since the Roman Empire.

The process of Islam expansion has also produced the great Islamic Empires of the Umayyads, Abbasids, Fatimids, the Muwahhidun of North Africa and Iberia, the Ottoman in the Middle East and the Balkans, and the Moghuls of India.

Even after the Islamic empires were defeated and colonized, and from their point of view victimized and humiliated, the revived Islam continued to witness vast movement of volunteer Jihadis, flocking to Afghanistan, then to Iraq and Syria. In contemporary Islam, that movement has come to embrace large numbers of Western Muslims from Europe and the Americas, who have been swept by the exciting idea of a revived Caliphate.

Raphael Israeli grew up in Fes, Morocco, and had a French education. At 14, he moved to Jerusalem, Israel. Now retired, he was a professor of history at Hebrew University. The author of 55 books, Israeli wrote this book so he could investigate the roots of the phenomenon of ISIS and al-Qa'ida, "the modern manifestations of itinerant Jihadis."

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