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.
History of South Korea
South Korea's subsequent history is marked by alternating periods of democratic and autocratic rule. Civilian governments are conventionally numbered from the First Republic of Rhee Syngman to the contemporary Sixth Republic. The First Republic, arguably democratic at its inception, became increasingly autocratic until its collapse in 1960. The Second Republic was strongly democratic, but was overthrown in less than a year and replaced by an autocratic military regime. The Third, Fourth, and Fifth Republics were nominally democratic, but are widely regarded as the continuation of military rule. With the Sixth Republic, the country has gradually stabilized into a liberal democracy.