South Korea–United States relations
Following Japanese surrender at the end of the Second World War, the Allied Powers divided the Korean peninsula along the 38th Parallel with two occupation zones with the United States in the south, and the Soviet Union in the north that would later become North Korea. On August 15, 1948, the southern half of Korea declared independence as the Republic of Korea with Syngman Rhee as president. The United States recognized the Republic of Korea as an independent state on January 1, 1949 and diplomatic relations between two countries were established on March 25 in the following year.
Cross-border skirmishes and raids at the 38th Parallel escalated into open warfare when the North Korean forces invaded South Korea on June 25, 1950. The Korean War broke out when North Korea invaded South Korea. In response, 16 member countries of the United Nations, including the United States, came to the defense of South Korea. It was the first significant armed conflict of the Cold War with extensive deployment of American and other troops.
North Korea–South Korea relations
North Korea–South Korea relations is very special with high conflicts. Originally a single nation, the two nations have been divided since the Korean War in 1953. North Korea is an one-party state run by Kim's regime. South Korea was formerly govern by one-party military dictatorships until 1987 when it held direct elections till now. Both nations claim to represent Korea. Both nations joined the United Nations in 1991 and recognized by most of the member states in the United Nations. Since 1970s, both nations start informal diplomatic dialogues in order to reduce military tensions. Since North Korea develops nuclear weapons, which raise concern by the international communities. In 2000, President of South Korea Kim Dae-jung became the first president to visit North Korea, after 55 years of North-South divisions in the peninsula.