South Korea, officially the Republic of Korea, is a country in East Asia, constituting the southern part of the Korean Peninsula, and sharing a land border with North Korea. About 25 million people, around half of the country's population of 51 million, live in the Seoul Capital Area.
The Korean Peninsula was inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early 7th century BCE. Following the unification of the Three Kingdoms of Korea into Silla and Balhae in the late 7th century, Korea was ruled by the Goryeo dynasty and the Joseon dynasty. The succeeding Korean Empire was annexed in 1910 into the Empire of Japan. Japanese rule in Korea ended following the former's surrender in World War II, after which Korea was divided into two zones; a northern zone occupied by the Soviet Union and a southern zone occupied by the United States. After negotiations on reunification failed, the latter became the Republic of Korea in August 1948 while the former became North Korea.