Treat others how you want to be treated
Psychology is the correct answer
Pope Urban II calls the first crusade - this event was caused as Byzantine Emperor Alexius I made an appeal to Urban for assistance. Urban united Christian Europe to fight against the Turks to take back the Holy Land.
Urban degraded Muslims in speeches with exaggerating stories of anti-Christian acts, giving the united Christian Europe a common enemy and a promised reward.
The Christians were, however, initially beaten back due to inexperience and lack of discipline.
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