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 Japan–Korea relations
Since 1945, relations involve three states: North Korea, South Korea and Japan. Japan cut off Korea from Qing Chinese suzerainty and for Japan, a high priority in the late 19th century, fighting wars with those two countries on the issue. Japan took control of Korea with the Japan-Korea Annexation Treaty of 1910. When Japan was defeated in World War II, Soviet forces took control of the North, and American forces took control of the South, with the 38th parallel as the agreed-upon dividing line. South Korea became independent as of August 15, 1945, and North Korea as of September 9, 1945. In June 1950, North Korea invaded and almost conquered South Korea, but was driven back by the United Nations command, leading South Korean, American, European and international forces. North Korea was nearly captured, with the United Nations intending to rollback Communism there. However, China entered the war, pushed the UN forces out of North Korea, and a military stalemate resulted along the lines similar to the 38th parallel. An armistice was agreed on in 1953, which is still in effect, and the cease-fire line of that year remains the boundary between North and South.