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–United States relations
On September 9, 1948, Kim Il-sung declared the Democratic People's Republic of Korea; he promptly received diplomatic recognition from the Soviet Union, but not the United States. The U.S. did not extend, and has never extended, diplomatic recognition to the DPRK. Kim Il-Sung's anti-American rhetoric often asserted that the U.S. was a capitalist imperialist successor to Japan, a view the country still holds today. In December 1950, the United States initiated economic sanctions against the DPRK under the Trading with the Enemy Act, which lasted until 2008.