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.
Korean nationalism
Korean reunification (Korean: 남북통일) refers to the hypothetical future reunification of North Korea and South Korea under a single government. South Korea had adopted a sunshine policy towards the North that was based on the hope that one day, the two countries would be re-united in the 1990s. The process towards this was started by the historic June 15th North–South Joint Declaration in August 2000, where the two countries agreed to work towards a peaceful reunification in the future. However, there are a number of hurdles in this process due to the large political and economic differences between the two countries and other state actors such as China, Russia, and the United States. Short-term problems such as a large number of refugees from the North migrating into the South and initial economic and political instability would need to be overcome.