Diplomatic relations between South Korea and the United States commenced in 1949. The United States helped establish the modern state of South Korea, officially the Republic of Korea, and fought on its UN-sponsored side in the Korean War (1950–1953). During the subsequent decades, South Korea experienced tremendous economic, political and military growth. To date, the United States recognized the ROK as the sole legitimate government of Korea.

South Korea has a long military alliance with the United States, aiding the U.S. in every war since the Vietnam War, including the Iraq War. At the 2009 G20 London summit, then-U.S. president Barack Obama called South Korea "one of America's closest allies and greatest friends".President Obama Vows Strengthened U.S.-South Korea Ties 2 Apr 2009. Embassy of the United States, Seoul In 1987, South Korea was among the first batch of countries to be designated as a major non-NATO ally. In June 2023, South Korean president Yoon Suk Yeol said that he had upgraded the country's alliance with the United States to one that is "nuclear-based" in the face of North Korea's growing military threat.

According to a 2026 Pew Research poll, 45% of South Koreans had a favorable view of the United States, while 55% had a negative view. According to a 2018 Gallup poll, 77% of Americans had a favorable view of South Koreans, while 22% had a negative view.

Country comparison Leaders of South Korea and the United States from 1950

History Background

Following the United States expedition to Korea in 1871, the United States and Joseon established diplomatic relations under the 1882 Treaty of Peace, Amity, Commerce, and Navigation. In 1883, Joseon sent the first ever Korean special mission to the United States, also known in Korean as Bobingsa (). However, Japan assumed direction over Korean foreign affairs in 1905 and in 1910 began a 35-year period of colonial rule over Korea.

In 1945, Japan surrendered to the Allies at the end of World War II. The United States proposed to the USSR that they could share responsibility of the Korean peninsula, dividing the Korean peninsula at the 38th parallel into two occupation zones, with the United States in the South and the Soviet Union in the North. This was intended to be a temporary measure.

Each half was polarized politically: the USSR-backed North was led by the Communist Party, while U.S. General John Hodge handpicked far-right Syngman Rhee to lead the South. Initial talks in 1945–6 to achieve a unified, independent Korea were not successful. The U.S. petitioned the United Nations to find a resolution, and the UN concluded that elections should be held. In reality, only the South held an election, as the North refused to allow UN officials entry to supervise the election. Syngman Rhee was officially elected after ruling the South for several years already, and in turn Stalin's regime appointed Communist Kim Il-Sung without an election.

In 1948, two separate nations were established: the Republic of Korea (ROK) in the South, and the Democratic People's Republic of Korea (DPRK) in the North. On January 1, 1949, the United States officially recognized the Republic of Korea as the sole legitimate government of Korea and established diplomatic relations on March 25 of that year.

Korean War 1950-1953

Cross-border skirmishes and raids at the 38th Parallel escalated into open warfare when the North Korean forces started to invade South Korea on June 25, 1950. In response, 16 member countries of the United Nations, led by 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 U.S. and other troops. The Korean War was a major Cold War military clash fought up and down the peninsula of Korea, finally leading to a stalemate in 1953 that restored the boundaries to nearly what they were at the start, along the 38th parallel. The war was initiated by Kim Il-sung of the Democratic People's Republic of Korea (North Korea), with assistance from China and the Soviet Union were arrayed against the Republic of Korea (South Korea), supported by the United States of America and a multinational United Nations force. Stanley Sandler, "The Korean War: An Interpretive History," in Richard Jensen, John Davidann, and Yoneyuki Sugita, eds. Trans-Pacific Relations: America, Europe, and Asia in the Twentieth Century (Praeger, 2003) pp.149–169

The war began with an invasion by North Korea in June 1950, followed by an unexpected American entry. North Korean forces had pushed the South Koreans and Americans back into a small perimeter around the port of Pusan. In September 1950, an amphibious landing at Inchon, followed by a breakout from the Pusan Perimeter, turned the tide. The North Korean People's Army (NKPA) disintegrated as the allies moved north, with UN approval, to unify the country. Unexpectedly the Chinese then sent in large numbers of infantry, and in the bitter cold of November-January 1950-51 pushed the UN forces out of the north. Communist supply lines were fragile, especially in the face of heavy American bombing, so the lines stabilized close to the 38th parallel in 1951. Two more years of static warfare followed, with the issue of returning reluctant Communist prisoners of war held by the UN the major sticking point. Finally an armistice was reached in summer 1953; the prisoners were exchanged and fighting ended in an uneasy truce that continues into the 21st century.Carter Malkasian, The Korean War 1950-1953 (Taylor & Francis, 2001) online.For the diplomatic history see William Stueck, The Korean War: An International History (Princeton University Press, 1995).

The war was limited in size and scope, but casualties were heavy on both sides. In the U.S., the political consequences of the war contributed to the defeat of the Truman administration and his Democratic party in the 1952 election of General Dwight D. Eisenhower, the Republican candidate who promised to end the war. For Americans and Chinese it is a "forgotten war", neglected on the timeline between the twin cataclysms of World War II and Vietnam. For the Koreans it is the central event of their modern history, and efforts to reunify the land continue. Hong-Kyu Park, "American involvement in the Korean war." The History Teacher 16.2 (1983): 249-263. Robert Jervis, "The impact of the Korean War on the Cold War." Journal of Conflict Resolution 24#4 (1980): 563-592.

Origins of the South Korea–United States alliance

In 1953, following the end of the Korean War, the United States established a bilaterial alliance pact with South Korea.

Moreover, the "U.S. alliance with South Korea would consequently have three functions. First, it would serve as part of a network of alliances and military installations designed to ring the Soviet threat in the Pacific. Second, it would deter a second North Korean attack, with U.S. ground troops serving as the 'tripwire' guaranteeing U.S. involvement. Third, it would restrain the South from engaging in adventurism".

The United States and South Korea are allies under the 1953 Mutual Defense Treaty. Under the agreement, U.S. military personnel have maintained a continuous presence on the Korean peninsula.

Issues and recent history

U.S. military and the sex trade

In 1953, at the end of the Korean War, the number of prostitutes in South Korea was estimated as about 350,000, with about 60 percent working near U.S. military camps. In the post-Korean War period, the U.S. military continued to contribute significantly to the South Korean economy, providing an estimated 1 percent of the South Korean GNP in 1991, including the sex industry. Quoting the newsletter of My Sister's Place, July 1991, p. 8. Despite the world-wide growth of women's human rights advocacy since the 1990s, and the shift towards foreign workers providing sex services for U.S. troops, (particularly women trafficked from the Philippines and the former Soviet Union), prostitution via "juicy bars" remains an issue near U.S. bases in South Korea.

1992 Yun Geum-i murder

In 1992, Yun Geum-i, a 26-year-old woman, was brutally killed by a U.S. serviceman, Private Kenneth L. Markle, in Dongducheon. In August 1993, the U.S. government compensated the victim's family with a payment of about US$72,000. Markle was sentenced by a South Korean court to life imprisonment, later reduced to 15 years. Professor Katharine Moon notes that the murder was not unique, and did not spark a national debate about the presence of U.S. forces. However, it did become a "call to action" for some Koreans, and led to the establishment of the "National Campaign for the Eradication of Crimes by U.S. troops."

Environmental degradation

In July 2000, the Eighth U.S. Army apologized for an incident where formaldehyde, a toxic fluid, was released into the Han River in February of that year. In a report released in 2017 detailing spill incidents from 1995 to 2015 at the US garrison in Yongsan, South Korean environmentalist groups expressed concern about the lack of transparency and the possibility of continued water contamination, as well as who would take responsibility for cleanup of the site.

Yangju highway incident

On 13 June 2002, two 14-year-old South Korean schoolgirls were crushed to death by a 50-ton United States Army vehicle in Yangju. Anti-Americanism was pervasive after the driver and the navigator of the vehicle were both acquitted in U.S. courts-martial on charges of negligent homicide. There was resentment from protesters towards the U.S.–South Korea Status of Forces Agreement, which restricted South Korea from having jurisdiction over alleged crimes that occurred when American soldiers were on official duty. South Korean presidential candidate Lee Hoi-chang called on United States President George W. Bush to "apologize to soothe the pain of the Korean people and to prevent any escalation in anti-American sentiment". American ambassador to South Korea Thomas C. Hubbard apologized on behalf of Bush.Demick, Barbara (November 27, 2002). "Anti-Americanism Sweeps South Korea". Los Angeles Times.

2008 beef protests in South Korea

The Government of South Korea banned imports of U.S. beef in 2003 in response to a case of mad cow disease in Washington state. In 2008, protests were held against U.S. beef that were reminiscent of the student "pro-democracy" movements of the 1980s. Nevertheless, by 2010, South Korea had become the world's third largest U.S. beef importer. With its strong import growth, South Korea surpassed Japan for the first time to become the largest market for U.S. beef in Asia; in 2016, U.S. beef imports in Korea reached a value of $1 billion.S. Korea becomes world's third largest U.S. beef importer July 16, 2010. People's Daily

2015 attack on the United States Ambassador