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Spiritual Heart — Religion of Unity/“Crusades”
As a formal cause for those bloody campaigns they declared “liberation” of the “Holy Sepulcher” from Muslims.
Although, there was no such a thing as the “Holy Sepulcher” whatsoever: the body of Jesus was placed into a cave, where it remained only for three days, and then it disappeared…
Moreover, Muslims respected everything related to the life of Jesus Christ: they considered themselves continuers of His cause and regarded Him as a Messiah; it is written in the Quran (see ). They regarded Christians as their brothers and sisters, and invited them to visit their common holy places together. They even built hotels for Christian pilgrims  in Jerusalem. Muslims even sent symbolic keys from Jerusalem to their Christian brothers in Rome — as a symbol of friendship .
Therefore there was no necessity to “liberate” anything from anyone. The only motive for all those crimes was craving for pillage.
To incite “Christians” to mass murders and robberies, the “aggressive” promised them life-time indulgences for taking part in the “crusades”; they also allured them with the “innumerable riches” of Muslim countries.
Those who were setting out for the robberies were giving their lands, houses, cattle, and all property into “custody” or selling for nothing… To whom? — To the Church, of course…
The detailed account of the atrocities that “Christians” were committing on their way can be found in the books by M.A.Zaborov [87-89]. All “crusades” entailed the complete sacking of villages and cities, that those troops of the devil were encountering on their way, and murdering of their populations: hundreds of thousands of armed robbers needed food (like do soldiers of all armies that set out for a long campaign), but where were these people, who went on foot or on carriages for thousands of miles, supposed to find it?
Some “crusades” ended just after plundering and destruction of cities in “Christian” countries (including Constantinople). Others reached their goal, although at the cost of a great number of casualties on the side of the aggressor.
Even “child crusades” were organized (based on the belief that “innocent” boys and girls would cope with the task better). They resulted in tens of thousands of 12 year-old children having died or been sold into slavery by ship-owners.
What was the overall effect of the “crusades”? — They resulted in a drastic change of the attitude of Muslims towards “Christians”.
But those Muslims… saved people of Africa and Asia from the Inquisition.