The Crusader movement was one of the most important and significant phenomena in world history. And at the same time, we still do not have a clear and precise answer to the question of what the Crusades are. How did this idea come about? Who was considered a crusader in the Middle Ages? How many crusades were there? How and why did these military-religious expeditions end? Finally, what were the cultural and historical results of the crusading movement for the West and the East? The author of the book reflects on these and many other questions, revising some traditional points of view about this interesting era. S. I. Luchitskaya is a medievalist historian (Institute of General History of the Russian Academy of Sciences), studies Christian ideas about Islam, author of more than a hundred works on the history of the Middle Ages and medieval culture.