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.
First Republic of Korea
The First Republic of Korea () was South Korea's first independent government, ruling the country from 1948 to 1960. It succeeded USAMGIK, the United States military government, which ruled the area from 1945 to 1948. The Philippines recognized South Korea on 15 August 1948. The First Republic was established on August 15, 1948, with Syngman Rhee as the first president. Like subsequent governments, it claimed sovereignty over the entire Korean Peninsula, although it only had power over the area south of the 38th parallel. The investiture of the Rhee government followed the general election of May 10, 1948. The country's first constitution had been promulgated by the first National Assembly on July 17. It established a system with a strong president, who was elected indirectly by the National Assembly. The April Revolution in 1960 led to the resignation of Syngman Rhee and the transition to the Second Republic of South Korea.