In another place of his book, Dr. LeBon adds, The early Arab conquests might have blurred their common sense and made them commit the sorts of oppression which conquerors usually commit, and thus ill-treat the subdued and compel them to embrace the Faith they wanted to spread all over the globe. Had they done so, all nations, which were still not under their control, might have turned against them, and they might have suffered what had befallen the Crusaders in their conquest of Syria lately.
However, the early Caliphs[2], who enjoyed a rare ingenuity which was unavailable to the propagandists of new faiths, realized that laws and religion cannot be imposed by force. Hence they were remarkably kind in the way they treated the peoples of Syria, Egypt, Spain and every other country they subdued, leaving them to practise their laws and regulations and beliefs and imposing only a small Jizya[3] in return for their protection and keeping peace among them.
In truth, nations have never known merciful and tolerant conquerors like the Arabs!