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, with which it was united until its division by the Soviet Union and the United States in 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 most populous metropolitan area in the world.