In truth it was the Arab empire that was spread by the sword and it is as an Arab empire that Islam is maintained to this day in the form a religion largely invented to hold that empire together and subdue native populations. An unmitigated cultural disaster parading as God’s will. Religious minorities were always second-class citizens in this empire and were only tolerated on sufferance and in abject deference to their Arab/Muslim masters; for polytheists and unbelievers there was no tolerance at all; it was conversion or death.
