The United States sent its first envoy to Korea in 1883. The United States led the U.N. coalition that fought a war to defend South Korea after North Korea invaded it in 1950. South Korea and the United States first signed a mutual defense treaty in 1953 and have worked closely together ever since to provide security in the region and combat global threats.

Here is a brief timeline of U.S.-South Korean diplomatic history and cooperation since the mid-20th century.


Aerial view of mountain terrain at 38th parallel (© AP Images)
South Korean troops at a mountain lookout post along the 38th parallel (© AP Images)

Following Japan’s surrender at the end of World War II, the Korean Peninsula is divided at the 38th parallel into two occupation zones.


Douglas MacArthur sitting next to Syngman Rhee (© Charles Gorry/AP Images)
South Korean President Syngman Rhee (right) and General Douglas MacArthur, supreme allied commander in Japan, at the inauguration of the new republic in August 1948 (© Charles Gorry/AP Images)

The parties do not realize their hopes for a unified Korea and instead establish two separate nations: the Republic of Korea in the south and the communist Democratic People’s Republic of Korea in the north.


Soldiers walking on an airfield (© Max Desfor/AP Images)
U.S. Marines regained control of Seoul’s Kimpo airfield in September 1950, three months after the North Korean invasion. (© Max Desfor/AP Images)

North Korean forces invade the Republic of Korea. Led by the United States, a 16-country U.N. coalition undertakes South Korea’s defense while China enters the war on North Korea’s side.


Three men looking at a document (© George Sweers/AP Images)
South Korean President Syngman Rhee (right), after signing the mutual defense treaty that he said would deter aggression and strengthen world security (© George Sweers/AP Images)

An armistice ends the fighting, but the parties do not sign a peace treaty. The United States and the Republic of Korea sign their mutual defense treaty.


Donald Trump walking with Moon Jae-in at the White House (© Evan Vucci/AP Images)
President Trump and South Korean President Moon Jae-in at the White House on June 30, 2017 (© Evan Vucci/AP Images)

The first Korea-U.S. Free Trade Agreement enters into force in 2012; six years later President Trump and President Moon Jae-in sign a landmark, revamped free trade deal.


Donald Trump shaking hands with Moon Jae-in (© Andrew Harnik/AP Images)
President Trump and South Korean President Moon Jae-in clasp hands at the Blue House in Seoul on November 7, 2017. (© Andrew Harnik/AP Images)

President Trump pays the first state visit to Seoul by a U.S. president in 25 years.

Current day

U.S. and South Korean soldiers taking positions (© Lee Jin-man/AP Images)
U.S. Army and South Korean soldiers take positions during a live-fire exercise in 2015. (© Lee Jin-man/AP Images)

The two close allies coordinate their response to the North Korean nuclear threat and their efforts to achieve complete denuclearization of the Korean Peninsula.