Korean War

What Happened

On 25 June 1950, the Korean People's Army of North Korea crossed the 38th parallel and invaded South Korea. The United Nations Security Council, meeting while the Soviet Union's representative was absent, condemned the invasion and called on member states to help repel it. On 27 June 1950, President Harry S. Truman ordered US air and sea forces to aid South Korea.

Seoul fell to the North Korean advance on 28 June. By early August, the Republic of Korea Army and its allies had been pushed back to the Pusan Perimeter in the peninsula's southeast, holding a last strip of territory. On 15 September, United Nations forces landed at Inchon near Seoul, cutting North Korean troops and supply lines. UN forces broke out from the perimeter on 18 September, retook Seoul, and in October crossed into North Korea, capturing Pyongyang and advancing toward the Yalu River, the border with China.

On 19 October, the Chinese People's Volunteer Army crossed the Yalu and entered the war on the North's side. UN forces retreated from North Korea in December after the Chinese first and second offensives. Communist forces captured Seoul again in January 1951, then lost it two months later to a UN counter-offensive. After an abortive Chinese spring offensive, UN forces retook ground roughly up to the 38th parallel.

Armistice negotiations opened in July 1951 and dragged on for two years as the fighting became a war of attrition. Combat ended on 27 July 1953 with the signing of the Korean Armistice Agreement, which provided for the exchange of prisoners and created a 4-kilometre wide Demilitarized Zone along the frontline, with a Joint Security Area at Panmunjom.

Background

Korea had been a Japanese colony for 35 years until the end of the Second World War in 1945. The Soviet Union and the United States then divided the country into two occupation zones along the 38th parallel, intending a future independent state. Political disagreements prevented that, and in 1948 the two zones formed separate governments.

North Korea was led by Kim Il Sung from Pyongyang; South Korea by Syngman Rhee from Seoul. Both claimed to be the sole legitimate government of all of Korea. Through this period the two sides fought extensive border clashes, while Rhee's government suppressed communist uprisings at Jeju and Yeosu-Suncheon.

The war became part of the wider Cold War. The United Nations Command assembled forces from 21 countries, with the United States supplying around 90 per cent of military personnel. Among the participating states were the United Kingdom, Canada, Turkey, Greece, Thailand, the Philippines, Ethiopia, New Zealand and Luxembourg, alongside the Soviet Union and the People's Republic of China on the communist side.

Why It Mattered

The conflict killed around one million military personnel and an estimated 1.5 million to 3 million civilians. North Korea suffered devastating damage from UN bombing, which destroyed virtually all of its major cities, making it one of the most heavily bombed countries in history. Alleged war crimes on all sides include the mass killing of alleged communists by South Korea, the Seoul National University Hospital massacre by North Korea, and the carpet bombing of North Korea by the United Nations Command.

The fighting introduced forms of industrial warfare that shaped later conflicts: armoured offensives in the North's initial invasion and in later UN advances, tunnel warfare by Chinese forces, and the first large jet aircraft battles. Three engagements became emblematic — the Battle of Kapyong, the Battle of Changjin Reservoir and the Battle of Inchon.

No peace treaty has ever been signed. The armistice of 27 July 1953 halted combat but left the Korean Peninsula divided, and the Demilitarized Zone remains the frontier between North and South Korea.

The Name in Japanese

The Japanese name is 朝鮮戦争, read in kana as ちょうせんせんそう, romanised as Chōsen sensō.

The word breaks into two parts: 朝鮮 (Chōsen), the Japanese name for Korea, and 戦争 (sensō), meaning "war".

朝 — read here as ちょう (chō). The character depicts the sun rising through plants and means "morning" or "dynasty". It carries the sense of a new day, and by extension a ruling house.

鮮 — read here as せん (sen). The character means "fresh", "vivid" or "bright". Combined with 朝, it forms 朝鮮, the name Japan has long used for Korea. The pairing is an old geographic label rather than a description of the people or the peninsula's own name for itself.

戦 — read here as せん (sen). It means "war", "battle" or "to fight". The character combines a weapon radical with a phonetic element.

争 — read here as そう (sō). It means "to contend", "to dispute" or "strife". Together, 戦争 (sensō) is the standard Japanese word for war — a contest carried on by force.

Two points are worth noting for learners. First, the Japanese reading of 朝鮮 is Chōsen, not the Korean-derived name; in modern Japanese, North Korea is referred to as 北朝鮮 (Kita-Chōsen) and South Korea as 韓国 (Kankoku), so the older term 朝鮮 in this context reflects the historical period and the peninsula as a whole. Second, the word 戦争 uses the same 戦 found in 戦後 (sengo), "postwar" — a term that in Japan most often refers to the period after 1945, which is the world this war erupted into.

Key Figures

Kim Il Sung led North Korea from Pyongyang and ordered the invasion of 25 June 1950.

Syngman Rhee led South Korea from Seoul and claimed sole legitimacy over the whole peninsula.

Harry S. Truman, President of the United States, ordered US air and sea forces to aid South Korea on 27 June 1950.

The Chinese People's Volunteer Army crossed the Yalu River on 19 October 1950, bringing the People's Republic of China into the war on the North's side and reversing the UN advance.