Korean War

The Korean War (25 June 1950–27 July 1953) was a major armed conflict on the Korean Peninsula between North Korea and South Korea, each supported by powerful international allies. As one of the earliest proxy wars of the Cold War, it became a decisive confrontation between communist and non-communist forces in East Asia. Although large-scale hostilities ceased with an armistice in 1953, no peace treaty was ever signed, leaving the peninsula divided and the conflict technically unresolved.

Background: Japanese Rule and Allied Occupation

Korea had been under Japanese colonial rule from 1910 to 1945. Japanese authority suppressed political expression, co-opted Korean resources, and provoked resistance movements both within Korea and among exiled nationalist groups. Korean fighters served alongside both Chinese Nationalist and Chinese Communist forces during the Second World War.
At the Cairo Conference in 1943, Allied leaders agreed that Korea would “in due course” become independent. As the Second World War neared its end, the Soviet Union pledged at Yalta to join the war against Japan. After launching its offensive on 8 August 1945, Soviet forces quickly occupied northern Korea, while the United States landed in the south. With little preparation, two American officers, Dean Rusk and Charles Bonesteel, proposed the 38th parallel north as a temporary dividing line for the occupation zones. The Soviets halted their advance at this boundary and the peninsula was divided between two occupying powers.
In the southern zone, the United States established a military government under General John R. Hodge. In the north, the Soviet Union supported emerging communist structures under Kim Il Sung. With Cold War tensions rising, negotiations for a unified state stalled. By 1948, two separate governments were declared: the Democratic People’s Republic of Korea (DPRK) in Pyongyang and the Republic of Korea (ROK) in Seoul. Both governments claimed legitimacy over the entire peninsula.

Outbreak of War: The 1950 Invasion

Border clashes were frequent throughout 1949 and early 1950. On 25 June 1950, North Korea launched a full-scale invasion across the 38th parallel. The Korean People’s Army, trained and equipped by the Soviet Union, rapidly captured Seoul and pushed South Korean forces to a small defensive perimeter around Busan.
The United Nations Security Council, acting in the absence of the Soviet delegate, condemned the attack and authorised member states to assist the ROK. A multinational force, dominated by the United States, intervened under the banner of the UN Command (UNC). Twenty-one countries contributed personnel, with the United States providing around 90 per cent of combat forces.

UN Counteroffensive and Advance into the North

In September 1950 General Douglas MacArthur launched the Inchon landing, a bold amphibious operation that severed North Korean supply lines. UN and ROK forces quickly recaptured Seoul and advanced into North Korea, capturing Pyongyang in October. As UNC units approached the Yalu River, China warned that it would intervene if its security were threatened.

Chinese Intervention and Stalemate

On 19 October 1950, the Chinese People’s Volunteer Army (PVA) crossed the Yalu and entered the war. A series of offensives inflicted heavy losses on UN forces, forcing a withdrawal from North Korea. Chinese and North Korean troops recaptured Seoul in January 1951, marking the third change of control of the capital.
General Matthew Ridgway, succeeding MacArthur’s field commanders after the difficult winter retreat, reorganised UN forces. Operation Ripper retook Seoul in March 1951. By mid-1951 the front had stabilised near the 38th parallel. Both sides attempted limited offensives, but by late 1951 the conflict had become a war of attrition characterised by intense artillery duels and fortified hill battles such as Triangle Hill.

Armistice Negotiations and the DMZ

Armistice talks began in July 1951 at Kaesŏng and later moved to Panmunjom. Negotiations were lengthy, primarily due to disagreements over prisoner repatriation and the positioning of the ceasefire line. During this period heavy bombing campaigns devastated the North’s infrastructure. By some estimates, millions of civilians died, and many of Korea’s major cities were almost entirely destroyed.
The Korean Armistice Agreement was signed on 27 July 1953. It established:

• A Korean Demilitarized Zone (DMZ) along the final battle line
• A Joint Security Area at Panmunjom
• Provisions for prisoner exchange

The armistice halted active fighting but did not terminate the state of war, leaving the peninsula divided.

Casualties and Human Impact

The war caused immense human suffering. Military casualties exceeded one million, with China, both Koreas, and UN forces sustaining heavy losses. Civilian deaths totalled an estimated two to three million. Atrocities were committed by all sides, including massacres in both North and South Korea. The conflict displaced millions, created permanent separations of families, and left deep political and social scars.

Names and Regional Memory

The Korean War is remembered differently across regions:

• South Korea: 6.25 War or 6.25 Upheaval, marking the date of the invasion
• North Korea: Fatherland Liberation War
• China: War to Resist America and Assist Korea
• United States and UK: commonly referred to as The Korean War, and sometimes The Forgotten War due to its relative neglect in public memory compared to the Second World War and the Vietnam War

Legacy and Continuing Division

The Korean War cemented the division of the peninsula into two contrasting political systems. It accelerated the militarisation of the Cold War, strengthened US alliances in Asia, and established China as a major actor in regional geopolitics. The armistice line remains one of the most heavily fortified borders in the world.
Despite periodic diplomatic initiatives, no peace treaty has been signed. The conflict therefore endures as a frozen war, shaping security, diplomacy, and life on the Korean Peninsula for generations.
The Korean War remains a defining moment in twentieth-century history, illustrating the global reach of the Cold War and the enduring significance of the unresolved division of Korea.