United Nations Command in the context of "Collective security"

The Korean War (25 June 1950 – 27 July 1953) was an armed conflict on the Korean Peninsula fought between North Korea (Democratic People's Republic of Korea; DPRK) and South Korea (Republic of Korea; ROK) and their allies. North Korea was supported by China and the Soviet Union, while South Korea was supported by the United Nations Command (UNC) led by the United States. The conflict was one of the first major proxy wars of the Cold War.

After the end of World War II in 1945, Korea, which had been a Japanese colony for 35 years, was divided by the Soviet Union and the United States into two occupation zones at the 38th parallel, with plans for a future independent state. Due to political disagreements the zones formed their own governments in 1948. North Korea was led by Kim Il Sung in Pyongyang, and South Korea by Syngman Rhee in Seoul; both claimed to be the sole legitimate government of all of Korea. On 25 June 1950, the Korean People's Army (KPA), equipped and trained by the Soviets, launched an invasion of the south. In the absence of the Soviet Union's representative, the UN Security Council denounced the attack and recommended member states to repel the invasion. UN forces comprised 21 countries, with the United States providing around 90% of military personnel.

Douglas MacArthur (26 January 1880 – 5 April 1964) was an American general who served as a top commander during World War II and the Korean War, achieving the rank of General of the Army. He served with distinction in World War I; as chief of staff of the United States Army from 1930 to 1935; as Supreme Commander, Southwest Pacific Area, from 1942 to 1945 during WWII; as Supreme Commander for the Allied Powers overseeing the occupation of Japan from 1945 to 1951; and as head of the United Nations Command in the Korean War from 1950 to 1951. MacArthur was nominated for the Medal of Honor three times, and awarded it for his WWII service in the Philippines. He is one of only five people to hold the rank of General of the Army, and the only person to hold the rank of Field Marshal in the Philippine Army.

MacArthur, the son of Medal of Honor recipient Arthur MacArthur Jr., was raised on Army posts in the Old West. He was valedictorian of the West Texas Military Academy, and First Captain at the U.S. Military Academy at West Point, where he graduated first in his class in 1903. During the 1914 U.S. occupation of Veracruz, he conducted a reconnaissance mission for which he was nominated for the Medal of Honor. In 1917, he was promoted from major to colonel and became chief of staff of the 42nd (Rainbow) Division. On the Western Front during World War I, he rose to the rank of brigadier general, was again nominated for a Medal of Honor, and was awarded the Distinguished Service Cross twice and the Silver Star seven times. From 1919 to 1922, MacArthur served as Superintendent of the U.S. Military Academy, where he initiated a series of reforms. His next posting was in the Philippines, where in 1924 he was instrumental in quelling the Philippine Scout Mutiny. In 1925, MacArthur became the Army's youngest major general at the age of 45, and in 1930 was appointed Chief of Staff of the U.S. Army. He was involved in the controversial expulsion of the Bonus Army protesters in Washington, D.C., in 1932, and organized the Civilian Conservation Corps. In 1935, MacArthur was appointed Military Advisor to the Commonwealth of the Philippines. He retired from the Army in 1937, but continued as an advisor and as a Field Marshal in the Philippine Army from 1936.

The Korean Demilitarized Zone (Korean: 한반도/조선반도 비무장 지대) is a heavily militarized strip of land running across the Korean Peninsula near the 38th parallel north. The demilitarized zone (DMZ) is a border barrier that divides the peninsula roughly in half. It was established to serve as a buffer zone between the sovereign states of the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea) under the provisions of the Korean Armistice Agreement in 1953, an agreement between North Korea, China, and the United Nations Command.

The DMZ is 250 kilometers (160 mi) long and about 4 kilometers (2.5 mi) wide. There have been various incidents in and around the DMZ, with military and civilian casualties on both sides. Within the DMZ is a meeting point between the two Korean states, where negotiations take place: the small Joint Security Area (JSA) near the western end of the zone.

The Military Demarcation Line (MDL), sometimes referred to as the Armistice Line, is the land border or demarcation line between North Korea and South Korea. On either side of the line is the Korean Demilitarized Zone (DMZ). The MDL and DMZ were established by the Korean Armistice Agreement.

In the Yellow Sea, the two Koreas are divided by a de facto maritime "military demarcation line" and maritime boundary called the Northern Limit Line (NLL) drawn by the United Nations Command in 1953. The NLL is not described by the Korean Armistice Agreement.

The Korean Armistice Agreement (Korean: 한국정전협정; Hanja: 韓國停戰協定) is an armistice that brought about a cessation of hostilities of the Korean War. It was signed by United States Army Lieutenant General William Harrison Jr. and General Mark W. Clark representing the United Nations Command (UNC), North Korea leader Kim Il Sung and General Nam Il representing the Korean People's Army (KPA), and Peng Dehuai representing the Chinese People's Volunteer Army (PVA). The armistice was signed on 27 July 1953, and was designed to "ensure a complete cessation of hostilities and of all acts of armed force in Korea until a final peaceful settlement is achieved."

During the 1954 Geneva Conference in Switzerland, Chinese Premier and foreign minister Zhou Enlai suggested that a peace treaty should be implemented on the Korean peninsula. However, the US secretary of state, John Foster Dulles, did not accommodate this attempt to achieve such a treaty. A final peace settlement has never been achieved. The signed armistice established the Korean Demilitarized Zone (DMZ), the de facto new border between the two nations, put into force a ceasefire, and finalized repatriation of prisoners of war. The DMZ runs close to the 38th parallel and has separated North and South Korea since the Korean Armistice Agreement was signed in 1953.

The Joint Security Area (JSA, often referred to as the Truce Village or Panmunjom) is the only portion of the Korean Demilitarized Zone (DMZ) where North and South Korean forces stand face-to-face. The JSA is used by the two Koreas for diplomatic engagements and, until March 1991, was also the site of military negotiations between North Korea and the United Nations Command (UNC).

The JSA has been the site of numerous events and incidents since its establishment in 1953, the first of which was the repatriation of prisoners of war (POWs) after the cessation of hostilities, across the Bridge of No Return. In 2018, North and South Korean officials agreed to clear the JSA of all landmines, weapons and guard posts. This withdrawal was complete on October 25, 2018, and the JSA now just contains 35 unarmed security guards. It was further agreed that henceforth, the area will serve mainly as a tourist attraction. On November 6, 2018, it was announced that the UNC would transfer primary guard duties of the now demilitarized Joint Security Area to both North and South Korea.

William Kelly Harrison Jr. (September 7, 1895 – May 25, 1987) was a highly decorated officer in the United States Army with the rank of Lieutenant General. A graduate of the United States Military Academy, he rose through the ranks to brigadier general during World War II and distinguished himself in combat several times, while serving as the assistant division commander of the 30th Infantry Division during the Normandy Campaign and the Battle of the Bulge. Harrison was decorated with the Distinguished Service Cross, the second highest decoration of the United States military for bravery in combat, for his actions during Operation Cobra.

Following the War, Harrison remained in the Army and after several stateside assignments, he was ordered to the Far East, where he served as head of the United Nations Command armistice delegation in the Korean War. He participated in the truce talks, which concluded with the signing of the Korean Armistice Agreement on July 27, 1953. Harrison completed his career as the commanding general of U.S. Caribbean Command in early 1957.

Chang Myon (Korean: 장면; August 28, 1899 – June 4, 1966) was a South Korean statesman, educator, diplomat, journalist and social activist as well as a Roman Catholic youth activist. He was the only prime minister of the parliamentary Second Republic. In addition, during the First Republic he was the fourth and last vice president of South Korea. His art name was Unseok (운석). His English name was John Chang Myon (baptismal name, surname, given name, respectively).

Under Japanese rule, Chang worked in education as a school teacher, administrator, and principal. In 1948, he led the delegation of the Republic of Korea to the UN General Assembly. In 1949, he became the first ambassador of the Republic of Korea to the United States. In 1950, he successfully appealed to the United States and the UN to send troops to assist in the Korean War. On November 23, 1950, he was appointed the prime minister of the First Republic of Korea. From 1956 to 1960, he served as the vice president of the First Republic of Korea.

The Iowa class was a class of six fast battleships ordered by the United States Navy in 1939 and 1940. They were initially intended to intercept fast capital ships such as the Japanese Kongō-class battlecruisers and serve as the "fast wing" of the U.S. battle line. The Iowa class was designed to meet the Second London Naval Treaty's "escalator clause" limit of 45,000-long-ton (45,700 t) standard displacement. Beginning in August 1942, four vessels, Iowa, New Jersey, Missouri, and Wisconsin, were completed; two more, Illinois and Kentucky, were laid down but canceled in 1945 and 1958, respectively, before completion, and both hulls were scrapped in 1958–1959.

The four Iowa-class ships were the last battleships commissioned in the U.S. Navy. All older U.S. battleships were decommissioned by 1947 and stricken from the Naval Vessel Register (NVR) by 1963. Between the mid-1940s and the early 1990s, the Iowa-class battleships fought in four major U.S. wars. In the Pacific Theater of World War II, they served primarily as fast escorts for Essex-class aircraft carriers of the Fast Carrier Task Force and also shelled Japanese positions. During the Korean War, the battleships provided naval gunfire support (NGFS) for United Nations forces, and in 1968, New Jersey shelled Viet Cong and Vietnam People's Army forces in the Vietnam War. All four were reactivated and modernized at the direction of the United States Congress in 1981, and armed with missiles during the 1980s, as part of the 600-ship Navy initiative. During Operation Desert Storm in 1991, Missouri and Wisconsin fired missiles and 16-inch (406 mm) guns at Iraqi targets.