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.

1945

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.

1948

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.

1950

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.

1953

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.

2012-2018

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.

2017

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.

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