If it is domestic, of course it is the Kaiyuan era. There are no bandits in thousands of miles, Chang'an is merchants from all countries; the emperor has high laws and regulations, travelers travel thousands of miles, no need to carry weapons with them, a bucket of grain is five coins, and thousands of miles of fertile land are turned into golden waves. If it were the world, it would be a prosperous age of eternal happiness. Expedition to Mobei, quelling the pirates; opening the sea, banning black sails, and galloping 90,000 miles; fighting in Sri Lanka to capture the king alive, all the countries in the Middle East surrendered; traveling to North America, discovering Australia; merchants from all over the world came to Korea, and a quarter of the world's wealth flow with China.