Religious Persecution is most often a variant of Persecution, motivated by non-religious factors such as simple greed. Many religious leaders accumulate wealth and many "religious" persecutions stem from attempts by members of other faiths to redistribute that wealth to themselves. Similarly religious differences may parallel geographic and ethnic differences, as in the tenth century CE with the Christians of Europe and the Muslims of the Middle East. In this case a simple imperial expansion may be accompanied by hate rhetoric based on both ethnic and religious differences.
Special to the religious domain is persecution related to strict monotheism.
Prior to the Christian Era, Egypt, Greece, and Rome, along with most of the rest of the world, were pantheistic societies. Each family had their household gods, each city or other place had its special gods, and nations might have their own gods. It was tradition and in many places law to show respect to local gods when visiting. To enter Athens and refuse to show respect to Athena was tantamount to a declaration of personal enmity to the city and its people.
Strict Monotheism enters the picture with Akhenaten (1364-1347 BCE), Pharaoh of Egypt. He proclaimed that there was no god but Aten (Ra), and ordered all references to other gods in the kingdom demolished or excised, forbidding even the use of the plural form of their word for god. Since this had the effect of uniting all religious authority in the Pharaoh and the side-effect of impounding all the wealth of the other temples to his personal use, it is possible that non-religious factors played a part in his conversion. After Akhenaten's death Egypt reverted to pantheistic practice.
Shortly after the death of Akhenaten and also out of Egypt came monotheistic Judaism under Moses, its first great rule-giver. Among the ten commandments of the new religion was one that forbade absolutely any show of respect for any other god than its one true god. When Imperial Rome extended its reach to their area, varous conflicts arose. Judaism had generally been tolerant of non-Jews worshipping their own gods in private in Jewish territory, but Jewish leaders were divided in their reponse to the requirements of Roman Law. Sadducees believed that some participation in Roman public cults was acceptable, while Pharisees forbade any contact. Imperial Rome at first exempted Jews from the requirement to participate in public cults, though this exemption was removed in the Christian Era.
Another religious persecution undertaken by the Roman Republic involved Julius Caesar's conquest of Gaul. Caesar identified the Druids as a source of Celtic hostility to Rome and to Roman civilisation, and accordingly undertook their eradication. He gives a mostly unflattering albeit grudgingly respectful account of the Druids in his Gallic Wars; his account of their human sacrifices seems likely to have been exaggerated. He may have been motivated in part to invade the island of Britain at least in part to eliminate a stronghold of Druidism, and the later Roman author Tacitus gives a dramatic account of an assault on the island of Anglesey, a Druid stronghold.
Out of Judaism came Christianity, which because it was strictly monotheistic and also encouraged conversion was a much more powerful threat to the established pantheistic order than had been Judaism. The Jewish exemption from the requirement to participate in public cults was lifted and the anti-monotheistic religious persecution of the Christians began under Nero.
By the eight century Christianity had attained a clear ascendancy in Europe and neighboring regions and a period of consolidation began marked by the pursuit of heretics and various other forms of monotheistic religious persecution. The Crusades bear mention as probably motivated more by greed and imperialism than by simple religious friction. Christian monotheistic religious persecution perhaps reached its apex with the Inquisition.
Also notable was the conquest of the Americas, where Christian societies suddenly found themselves easily dominating a vast and complex set of pantheistic civilizations. This was a period of extreme religious persecution, primarily forced conversion, and the destruction of cultural materials (motivated in part because native writing was pictographic: see The Catholic crusade against the imagination).
Meanwhile south and east of the Christian empires yet another strict monotheism had arisen: Islam. Generally following the Jewish tradition of tolerance towards non-believers provided they maintained the outward habits of believers, Muslims spread across northern Africa, the middle east, northern India, and adjoining regions.
[needs some more work]
