As the Mongol empire unravels, its fragments get absorbed by the cultures it once attacked. Its eastern half becomes the Yuan Dynasty, which falls to Ming who go on to fortify the Great Wall and become the most stable and prosperous order on the planet. Meanwhile, the western Khans adopt Islam, with their most powerful faction settling in Persia.
By the 13th century, the rest of the region was falling under the rule of the Mamluks, a professional warrior caste that became the heart of the Ottoman Empire. Their capture of Constantinople in 1458 isolated western Europe once again, threatening its burgeoning renaissance. But not before the world’s best geographical and navigational knowledge had made its way in.
Understanding the value of circumventing overland routes, Portugal’s prince Henry the Navigator, had been making a sustained effort to find a way to China by sea in what proved to be the greatest test of Ptolemy’s scheme.