South Korea, officially the Republic of Korea is an East Asian state on the southern half of the Korean Peninsula. To the north, it is bordered by North Korea (Democratic People's Republic of Korea), with which it was a single country called Korea until 1945. To the west, across the Yellow Sea, lies China, and to the southeast, across the Korea Strait, lies Japan. Approximately one-half of South Korea's population lives in or near the capital and largest city, Seoul, the second largest metropolitan area in the world. After its founding in 1948, the country has struggled with the aftermath of 35 years of Japanese occupation, the Korean War, and decades of military rule, seeing five major constitutional changes. Pro-democracy demonstrations during the 1980s led to free elections in 1987. South Korea is now a multi-party democracy.