In order to follow the course of the spread of Islam westward into Central Asia, we must retrace our steps to the period of the first Arab conquests.

By the middle of the seventh century, the great dynasty of the Sāsānids had fallen, and the vast empire of Persia that for four centuries had withstood the might of Rome and Byzantium, now became the heritage of the Muslims.

When the armies of the state had been routed, the mass of the people offered little resistance; the reigns of the last representatives of the Sāsānid dynasty had been marked by terrible anarchy, and the sympathies of the people had been further alienated from their rulers on account of the support they gave to the persecuting policy of the state religion of Zoroastrianism.

The Zoroastrian priests had acquired an enormous influence in the state; they were well-nigh all-powerful in the councils of the king and arrogated to themselves a very large share in the civil administration. They took advantage of their position to persecute all those religious bodies—(and they were many)—that dissented from them. Besides the numerous adherents of older forms of the Persian religion, there were Christians, Jews, Sabæans and numerous sects in which the speculations of Gnostics, Manichæans and Buddhists found expression.

In all of these, persecution had stirred up feelings of bitter hatred against the established religion and the dynasty that supported its oppressions, and so caused the Arab conquest to appear in the light of a deliverance.^[2] The followers of all these varied forms of faith could breathe again under a rule that granted them religious freedom and exemption from military service, on payment of a light tribute...

To the distracted Christian Church in Persia the change of government brought relief from the oppression of the Sāsānid kings, who had fomented the bitter struggles of Jacobites and Nestorians and added to the confusion of warring sects.

Some reference has already been made to earlier persecutions, and even during the expiring agony of the Sāsānid dynasty, Khusrau II, exasperated at the defeat he had suffered at the hands of the Christian emperor, Heraclius, ordered a fresh persecution of the Christians within his dominions, a persecution from which all the various Christian sects alike had to suffer.

These terrible conditions may well have prepared men's minds for that revulsion of feeling that facilitates a change of faith. ‘Side by side with the political chaos in the state was the moral confusion that filled the minds of the Christians; distracted by such an accumulation of disasters and by the moral agony wrought by the furious conflict of so many warring doctrines among them, they tended towards that peculiar frame of mind in which a new doctrine finds it easy to take root, making a clean sweep of such a bewildering babel and striving to reconstruct faith and society on a new basis.

In other words the people of Persia, and especially the Semitic races, were just in the very mental condition calculated to make them welcome the Islamic revolution and urge them on to enthusiastically embrace the new and rugged creed, which with its complete and virile simplicity swept away at one stroke all those dark mists, opened the soul to new, alluring and tangible hopes, and promised immediate release from a miserable state of servitude.^[3] But the Muslim creed was most eagerly welcomed by the townsfolk, the industrial classes and the artisans, whose occupations made them impure according to the Zoroastrian creed, because in the pursuance of their trade or occupations they defiled fire, earth or water, and who thus, outcasts in the eyes of the law and treated with scant consideration in consequence, embraced with eagerness a creed that made them at once free men, and equal in a brotherhood of faith.^[4]

Nor were the conversions from Zoroastrianism itself less striking : the fabric of the National Church had fallen with a crash in the general ruin of the dynasty that had before upheld it; having no other centre round which to rally, the followers of this creed would find the transition to Islam a simple and easy one, owing to the numerous points of similarity in the old creed and the new...

That this widespread conversion was not due to force or violence is evidenced by the toleration extended to those who still clung to their ancient faith. Even to the present day there are some small communities of fire-worshippers to be found in certain districts of Persia, and though these have in later years often had to suffer persecution,^[5] their ancestors in the early centuries of the Hijrah enjoyed a remarkable degree of toleration, their fire-temples were respected, and we even read of a Muhammadan general (in the reign of al-Mu'taṣim, A.D. 833-842), who ordered an imām and a mu'adhdhin to be flogged because they had destroyed a fire-temple in Sughd and built a mosque in its place.^[6]

In the tenth century, three centuries after the conquest of the country, fire-temples were to be found in 'Irāq, Fārs, Kirmān, Sijistān, Khurāsān, Jibāl, Ādharbayjān and Arrān, i. e. in almost every province of Persia.^[7] In Fārs itself there were hardly any cities or districts in which fire-temples and Magians were not to be found.^[8] Al-Sharastānī also (writing as late as the twelfth century), makes mention of a fire-temple at Isfīniyā, in the neighbourhood of Baghdād itself.^[9]

In the face of such facts, it is surely impossible to attribute the decay of Zoroastrianism entirely to violent conversions made by the Muslim conquerors.

The number of Persians who embraced Islam in the early days of the Arab rule was probably very large from the various reasons given above, but the late survival of their ancient faith and the occasional record of conversions in the course of successive centuries, render it probable that the acceptance of Islam was both peaceful and voluntary