Korea annually celebrates Ocean Day on May 31. May 31 is the day when General Jang Bogo of Silla established the Cheonghaejin garrison. Naval hero Jang Bogo safeguarded Silla’s international trade by building Cheonghaejin on today’s Wando in Jeollanamdo and sweeping pirates from the sea. He was regarded as the king of the ocean because he built a maritime trade network that connected Silla, Tang China, and Japan with Cheonghaejin as a trading hub and promoted trade with many other countries, including those in Southeast Asia and Arabia. Many heroes appeared throughout Korean, Chinese, and Japanese history, but it is rare to find heroes who were documented in the history of all three countries. Jang Bogo is one of them. The New Book of Tang, an old Chinese history book, commended Jang Bogo for his courage, and famous Tang poet Du Fu described Jang as intelligent and the most successful man in the orient. Also, Japanese Buddhist priest Ennin admired Jang and thanked him for helping his passage to China. On China’s Shandong Peninsula, there is a Jang Bogo memorial and museum, built by the Chinese government. In Japan, there are temples that deify Jang Bogo. Edwin Reischauer, who served as the American ambassador to Japan and a professor at Harvard University, described Jang as “the trade prince of the maritime commercial empire” in his book, Ennin’s Travels in Tang China. Jang Bogo was a fearless trade king, who built Korea’s first maritime commercial empire.