The Korean War: The Cold War in East Asia

The Korean War (한국전쟁, Hanguk Jeonjaeng), was a three-year-long proxy war between North Korea (DPRK) and South Korea (ROK) from June 1950 to July 1953, instigated by the invasion of ROK by DPRK forces on 25 June 1950. The war is also known as the Forgotten War; having succeeded World War II and preceded the Vietnam War, there was little public attention due to its relatively minor scale.

Although an armistice was signed on 27 July 1953, the two countries technically remain at war without a peace treaty. The North Koreans were supported by the Chinese and Soviets, whereas the South Koreans by the United States and the United Nations. That said, we will discuss what caused the war and how the war progressed.


For centuries, Korea was constantly under the domination of foreign powers. This includes early in the 20th Century, where Korea was under the annexation of imperial Japan for 35 years up till the surrender of Japan and the end of World War II in 1945. Subsequently, Korea was divided along the 38th Parallel – the north administered by the Soviets, and the south by Americans. The two zones then gained independence, with the south on 15 August 1948 and the north shortly after, on 9 September 1948. Due to Soviet influence, the north was established as a totalitarian communist state under the former Major of the Soviet Red Army, Kim Il Sung. Similarly, the south was established as a capitalist state under the leadership of Syngman Rhee as a result of American influence.

Korea was significant to the communist bloc, which aimed to expand its influence in the Asia-Pacific. While the Soviet Union had numerous satellite states in Eastern Europe, it only had China as an ally in the Asia-Pacific. With North Korea, the communist bloc would then have a platform to influence other countries within the region and counterbalance American influence in neighbouring Japan.

Both the ROK and DPRK government retained their claims on being the only legitimate government of Korea and sought to reunite Korea under their respective ideologies. From 1948 to 1950, recurrent clashes along the border were initiated by ROK forces under Syngman Rhee, who even expressed his desire to invade the north and reunite Korea. However, he did not take any significant actions towards that desire.

Outbreak of the War

On the morning of 25 June 1950, the DPRK military, or the Korean People’s Army (KPA), crossed the border behind artillery fire, claiming that troops from the south had attacked them first. Fighting initially ensued in Ongjin before KPA forces began to attack along the entire border. Within three days, Seoul fell. Syngman Rhee then fled Seoul together with some of the ROK government. The UN Security Council denounced the invasion and formed the UN Command to be dispatched to Korea.

The South Koreans lacked troops and arms as the US was fixated on rebuilding Europe after World War II and were unprepared for the war in Korea. The US saw Japan as a strategic base to thwart the spread of communism in East Asia, which led them to finalise their decision to engage in the war.

Early into the War

The Americans’ first vital engagement in the Korean War was at the Battle of Osan. However, as they lacked weapons that could destroy North Korean tanks, the Americans were crushed by KPA forces. KPA forces could progress southwards, pushing back ROK forces and American forces by August 1950. North Korean forces then squeezed UN forces into a small corner of the south-eastern part of Korea, also known as the Busan Perimeter, by September. However, they were able to repel attacks from the KPA. Reinforcements were sent from Japan and the US mainland to Busan, enabling the UN to gather their forces and outnumber the KPA.

American forces then attempted to make an amphibious landing at Incheon, which aimed to relieve the UN forces centred in Busan and disrupt the supply lines of the KPA. The landing at Incheon faced little resistance as few North Korean defenders were positioned there.

By early October that year, the KPA was repelled by the UN Command across the border back into North Korean territory. Pyongyang subsequently fell to US forces on 19 October 1950, advancing towards the Chinese border. This triggered Chinese troops, or the People’s Volunteer Army (PVA), to cross the Yalu River clandestinely on the same day. The First Phase Offensive was initiated six days later and resulted in the retreat of the UN Command.

The UN offered the Chinese government a ceasefire after the Battle of the Ch’ongch’on River on 11 December 1950. However, the Chinese rejected the ceasefire as they were convinced of the indomitability of the PVA after the numerous recent battles. By late December, Chinese forces had entered South Korean territory.

Subsequently, UN forces retreated to Suwon, Wonju, and the area north of Samcheok. The battlefront was held along these positions, causing the PVA to suffer depletions in their supplies. After finding that the PVA abandoned their battle lines in January 1951, a full-scale advance known as Operation Thunderbolt allowed the UN forces to recapture the city of Wonju and reach the Han River.

Subsequent Battles

Operation Killer succeeded Operation Thunderbolt from mid-February to kill as many communist troops as possible. As such, the place south of the Han River and the city of Hoengseong was re-occupied by American forces. Subsequently, Operation Ripper effectively expelled communist forces from Seoul by mid-March.

In late March, the UN forces were reorganised, and Operations Courageous enabled them to advance to the Kansas Line, north of the 38th Parallel. This was followed by a PVA counterattack in April, with the fierce Battle of the Imjin River and the Battle of Kapyong. This triggered the counterattack by the Americans, who reclaimed the Kansas Line on 12 May 1951.

From July 1951 till the end of the Korean War in July 1953, The North and the South exchanged little territory despite the skirmishes between UN forces and PVA-KPA forces. North Korean territory continued to be heavily bombed while negotiations for an armistice were underway in Kaesong. The UN aimed to recapture the entirety of South Korean territory and minimise the loss of territory. The two sides continued to trade artillery fire along the battlefront with American advantage.

The PVA attempted a final offensive in the last couple of weeks before the end of the war to allow them to capture territory for the DPRK. While the Chinese were slightly successful in penetrating ROK lines, they ultimately failed to capitalise as the US forces overwhelmed them with firepower in retaliation.

In the course of the war, Seoul was captured by communist forces five times. The front stabilised to around the 38th Parallel for the last two years, and there were minimal changes in territory. However, air combat sustained throughout the war, and the US continued to bomb DPRK territory relentlessly.

Armistice and Aftermath

After dragging the negotiations on for two years, from Kaesong to Panmunjom, Both sides signed the Korean Armistice Agreement on 27 July 1953. This was slightly over three years since the commencement of the war. While the DPRK continued to claim victory of the war, the absence of a peace treaty meant there was no resolution. The Korean Demilitarised Zone was established and remained patrolled by forces from both countries and the UN Command. From July to November 1954, both countries were involved in an exchange of dead combatants known as Operation Glory. Outside of Korea, the war resulted in a significant impact on US foreign policy.

The Korean War caused a total of about three million casualties. This includes a civilian death rate more significant than either World War II or the Vietnam War. Many cities on both sides of the border were obliterated, and the governments of both countries committed countless war atrocities. The effects of the war can still be felt in both North and South Korea today, especially among the elderly. With that, we hope that there may someday be a peaceful reunification on the Korean peninsula.

Akshay Dinesh

As a student, I am passionate about writing articles that educate and guide others. I have a diverse range of interests and try to cover a variety of topics in my writing. If you have any questions, please feel free to contact me at akshay[at]

Add comment

Book Your Free Class

Like what we do?

Consider donating to us. Running a free educational website has its costs. We never charge our users a fee to access our content. However, we still have to foot our bills. Please help us do more. Any amount is appreciated.