The Islamic caliphate that ruled from Baghdad from 750 to 1258 CE — overthrowing the Umayyads through a revolutionary movement, governing the largest empire of its era, presiding over the Islamic Golden Age of science, philosophy, and medicine, and ending with the Mongol sack of Baghdad that destroyed the caliphate's political and cultural center.
In 830 CE, the Caliph al-Ma'mun established the House of Wisdom in Baghdad — an institution that collected, translated, and built upon every text of Greek, Persian, Indian, and Syriac knowledge that could be found. Within a century, Arab scholars had translated virtually all of Aristotle, Euclid, Galen, and Ptolemy, had developed algebra and decimal arithmetic, had made foundational contributions to optics and medicine, and had preserved philosophical texts that would otherwise have been lost. This was not scholarship for its own sake. It was a civilization deciding that all human knowledge was Islamic knowledge — that truth, wherever found, belonged to the tradition. That decision changed the world.