Obviously, a land socially atomized and politically split into many principalities was destined to fall before the first strong invader. This invader was Islam. The Mohammedans attacked India soon after their conquest of Persia, but these early attacks were mere border raids without lasting significance. The first real Mohammedan invasion was that of Mahmud of Ghazni, an Afghan prince, in A.D. 1001. Following the road taken by the Aryans ages before, Mahmud conquered north-western India, the region known as the Punjab. Islam had thus obtained a firm foothold in India, and subsequent Moslem leaders spread gradually eastward until most of northern India was under Moslem rule. The invaders had two notable advantages: they were fanatically united against the despised "Idolaters," and they drew many converts from the native population. The very antithesis of Brahminism, Islam, with its doctrine that all Believers are brothers, could not fail to attract multitudes of low-castes and out-castes, who by conversion might rise to the status of the conquerors. This is the main reason why the Mohammedans in India to-day number more than 70,000,000--over one-fifth of the total population. These Indian Moslems are descended, not merely from Afghan, Turkish, Arab, and Persian invaders, but even more from the millions of Hindu converts who embraced Islam. For many generations the Moslem hold on India was confined to the north. Then, early in the sixteenth century, the great Turko-Mongol leader Baber entered India and founded the "Mogul" Empire. Baber and his successors overran even the south, and united India politically as it had never been united before. But even this conquest was superficial. The Brahmins, threatened with destruction, preached a Hindu revival; the Mogul dynasty petered out; and at the beginning of the eighteenth century the Mogul Empire collapsed, leaving India a welter of warring principalities, Mohammedan and Hindu, fighting each other for religion, for politics, or for sheer lust of plunder.