Post-classical history (also called the Postclassical Era) is the period of time that immediately followed ancient history. Depending on the continent, the era generally falls between the years AD 200-600 and AD 1200–1500. The major classical civilizations the era follows are Han China (ending in 220), the Western Roman Empire (in 476), the Gupta Empire (in the 550s), and the Sasanian Empire (in 651). The post-classical era itself was followed by the early modern era, and forms the middle period in a three-period division of world history: ancient, post-classical, and modern. The era is thought to be characterized by invasions from Central Asia, the development of the great world religions (Christianity, Islam, and Buddhism), and of networks of trade and military contact between civilizations.The name of this era of history derives from classical antiquity (or the Greco-Roman era) of Europe. In European history, ""post-classical"" is synonymous with the medieval time or Middle Ages, the period of history from around the 5th century to the 15th century. In Europe, the fall of the Western Roman Empire saw the depopulation, deurbanization, and limited learning of the ""Dark Ages"" (except in Eastern Mediterranean Europe, where the Eastern Roman Empire flourished until 1204), but gradually revived somewhat under the institutions of feudalism and a powerful Catholic Church. Art and architecture were characterized by Christian themes. Several attempts by the Crusades to recapture the Holy Land for Christianity were unsuccessful.In Asia, the depredations of the Dark Ages were avoided, at least in the west, where the Spread of Islam created a new empire and civilization with trade between the Asian, African, and European continents, and advances in science. East Asia experienced the full establishment of power of Imperial China (after the interregnum chaos of the Six Dynasties), which established several prosperous dynasties influencing Korea, Vietnam, and Japan. Religions such as Buddhism and Neo-Confucianism spread. Gunpowder was originally developed in China during the post-classical era. The invention of gunpowder led to the invention of fireworks, then to its use in warfare. Also, the invention spread around the world. The Mongol Empire greatly affected much of Europe and Asia, the latter of which was conquered in many areas. The Mongols were able to create safe trade and stability between the two regions, but inadvertently encouraged the spread of the Black Plague.The timelines of the major civilizations of the Americas—Maya (AD 250 to 900), the Aztec (14th to 16th centuries), and the Inca (1438 to 1533)—do not correspond closely to the Classical Age of the Old World.Outstanding cultural achievement in the post-classical era include books like the Code of Justinian,The Story of the Western Wing, and The Tale of Genji; the mathematics of Fibonacci, Oresme, and Al-Khwārizmī; the philosophy of Avicenna, Thomas Aquinas, Petrarch, Zhu Xi, and Kabir; the painting of Giotto, Behzād, and Dong Yuan; the astronomy of Nasir al-Din al-Tusi and Su Song; the poetry of Rumi, Dante, Chaucer, and the Li Bai; the travels of Marco Polo and Ibn Battuta; the historiography of Leonardo Bruni and Ibn Khaldun; and the architecture of places like Chartres, the Mezquita, Angkor Wat, and Machu Picchu.