Between the 10th and 11th centuries, the population of China doubled in size to around 100 million people, mostly because of the expansion of rice cultivation in central and southern China, and the production of abundant food surpluses. The Song dynasty also saw a revival of Confucianism, in response to the growth of Buddhism during the Tang, and a flourishing of philosophy and the arts, as landscape art and porcelain were brought to new levels of maturity and complexity. However, the military weakness of the Song army was observed by the Jurchen Jin dynasty. In 1127, Emperor Huizong of Song and the capital Bianjing were captured during the Jin–Song Wars. The remnants of the Song retreated to southern China.