While time of Mongol rule is called a dynasty, it was in fact a government of occupation. While the Mongols did use existing governmental structures for the duration, the language they used was Mongol, and many of the officials they used were non-Chinese. Mongols, Uygurs from central Asia, some Arabs and even an Italian named Marco Polo all served as officials for the Mongol government. One of the more significant accomplishments of the Mongol tenure was the preservation of China as we know it in that China wasn't turned into pastureland for the Mongolian ponies, which not only was common Mongolian practice for territories they'd overrun but had actually been advocated by some of the conquering generals. The Yuan dynasty also featured the famous Khubilai Khan, who, among other things, extended the Grand Canal. While in many ways, the Yuan was a disaster, the reluctance of the Mongols to hire educated Chinese for governmental posts resulted in a remarkable cultural flowering; for example, Beijing Opera was invented during the Yuan. On the other hand, attempts to analyze the failure of the Song in keeping barbarians out China led to the rise and dominance of Neo-Confucianism, a notoriously conservative (if not outright reactionary) brand of Confucianism that had originally developed during the Song.