Within the century of the establishment of Islam upon the Arabian Peninsula and the subsequent rapid expansion during the early Muslim conquests, one of the most significant empires in world history was formed. For the subjects of this new empire, formerly subjects of the greatly reduced Byzantine Empire and obliterated Sasanian Empire, not much changed in practice. The objective of the conquests was mostly of a practical nature, as fertile land and water were scarce in the Arabian Peninsula. A real Islamization therefore only came about in the subsequent centuries.