Why the South Korean Army Collapsed at the Outbreak of the Korean War: Failed Leadership, Poor Personnel Decisions, and Inadequate War Preparedness

When North Korea launched its invasion on June 25, 1950, the Republic of Korea (ROK) Army was forced to retreat south after losing Seoul in just three days.

The surprise attack by the North Korean People's Army was a major factor behind the rapid collapse. However, historians have also pointed to the composition of the ROK military leadership and the country's level of war preparedness as important contributing factors to the early defeats.

1. Personnel Issues within the ROK Military Leadership

At the time, President Syngman Rhee appointed Shin Sung-mo as Minister of National Defense and Chae Byeong-deok as Chief of Staff of the ROK Army. 

Shin Sung-mo was a former merchant ship captain with limited military experience, while Chae Byeong-deok had spent most of his career in ordnance and had relatively limited experience commanding large-scale field operations.

In contrast, the ROK Army included several highly capable officers, such as Kim Seok-won, Kim Hong-il, and Lee Hyung-geun, who had gained extensive combat experience in the Imperial Japanese Army and on the Chinese front during the Second Sino-Japanese War. They were widely regarded as principled and outspoken officers who were not inclined to flatter their superiors, and it has been suggested that these characteristics prevented them from gaining President Rhee's full confidence.

Subsequent military historical studies have frequently argued that these personnel decisions had a negative impact on the ROK Army's wartime preparedness and the effectiveness of its command structure during the initial stages of the Korean War.

2. Repeated North Korean Provocations and Misjudgment

In the period leading up to the outbreak of the Korean War, North Korea reportedly carried out approximately 847 armed provocations along the 38th Parallel, most of them concentrated near the border. 

However, the ROK military leadership failed to fully recognize that these incidents could have been part of a deliberate strategy to prepare for a future full-scale invasion.

The North Korean Army followed a recurring pattern. Its forces would cross the 38th Parallel, engage in limited clashes with ROK troops, and then withdraw to the north. Because the ROK Army repeatedly gained the upper hand in these border skirmishes, many officers came to underestimate the true combat capability of the North Korean military. As a result, an overly optimistic belief emerged within parts of the military leadership that the ROK Army would be capable of advancing northward if war broke out. Consequently, vigilance against the possibility of a large-scale invasion gradually weakened, and some military historians have argued that the ROK Army's defensive posture became increasingly complacent.

At the time, Chief of Staff Chae Byeong-deok made remarks suggesting that, if ordered to advance north, the ROK Army could quickly reach Pyongyang:

"There have been countless provocations by the North Korean People's Army along the 38th Parallel. However, our brave ROK soldiers have repelled every one of them. The combat capability of the ROK Army is now the strongest in the Far East, and even the American military advisers share this assessment. Therefore, if our army is simply given the order to advance north, we could have lunch in Pyongyang and dinner in Sinuiju. Some people criticize our defensive posture, but such individuals are engaging in acts that undermine the nation."

In reality, however, North Korea had already been preparing for a full-scale invasion with extensive Soviet support, centering its offensive on T-34 tanks and large armored formations. Border skirmishes and full-scale conventional warfare were fundamentally different in nature.

The circumstances surrounding Chae Byeong-deok's dismissal as Chief of Staff unfolded shortly after the fall of Seoul. During an inspection of the Han River defensive line, General Douglas MacArthur and his subordinate, Major General Edward Almond, met with Chae and asked, "How do you intend to defend the country now? As Chief of Staff, what is your operational plan?" President Syngman Rhee was also present during the meeting.

According to historical accounts, Chae replied that if two million South Korean young men were conscripted and trained, they would be able to repel the invasion. His response was widely interpreted as demonstrating that he had not fully grasped the severity and urgency of the military situation.

To make matters worse, Chae spoke very little English, and communication had to proceed through an interpreter, causing his already unsatisfactory briefing to be repeatedly interrupted. According to several historical accounts, MacArthur became deeply disappointed and reportedly remarked to Major General Almond that Chae was "beyond help."

Nevertheless, MacArthur handled the situation diplomatically. Rather than openly criticizing Chae during the meeting, he publicly praised him. Later that evening, however, MacArthur requested a private meeting with President Rhee. During their conversation, he reportedly expressed strong dissatisfaction with Chae's performance and urged Rhee to remove him from his position.

According to this interpretation of the historical record, Chae Byeong-deok was dismissed because he was judged by MacArthur to be incapable of effectively commanding the ROK Army during the crisis, rather than because he voluntarily resigned and accepted responsibility for the military setbacks.

3. The Pollack Incident

Under the agreement reached by the U.S.–Soviet Joint Commission in February 1946, trade between North and South Korea continued until March 1949. During this period, however, the two sides managed trade quite differently. In the South, there was no centralized control mechanism, allowing various goods—including medicines, electrical equipment, and other materials with potential military applications—to be shipped to the North. In contrast, the North operated a formal trade control system and mainly sent food products such as pollack, squid, and salted mackerel to the South.

After assuming command of the 1st Infantry Division in January 1949, Brigadier General Kim Seok-won became increasingly concerned about this situation and ordered trade at the inter-Korean trading post under his jurisdiction to be suspended. Nevertheless, the exchanges reportedly continued with the tacit approval of Army Chief of Staff Chae Byeong-deok. In mid-April of the same year, Kim ordered the seizure of more than twenty trucks carrying pollack that had crossed from North Korea through the Toseong area.

Upon receiving the report, Chief of Staff Chae repeatedly ordered that the confiscated goods be returned to their owners. Kim refused to comply. Instead, he sold the seized pollack and used the proceeds to purchase food, beverages, fruit, and candy, which were distributed to the soldiers and civilian laborers of the 1st Infantry Division, many of whom were suffering from food shortages.

Rather than directly reprimanding Kim—his senior from the Imperial Japanese Army Academy—Chae reportedly attempted to pressure him through other means. Enraged, Kim strongly protested, asking, "How can the Chief of Staff of the Army be trading with North Korea?" 

His objection reflected the belief that, while North Korea was actively preparing to threaten the Republic of Korea, those responsible for national defense should not be engaging in trade that could benefit the North.

Although inter-Korean trade at the time was conducted in accordance with government policy, dissatisfaction with the practice was widespread among frontline soldiers. The controversy intensified further as rumors circulated that Chief of Staff Chae was personally involved in the pollack trade and that part of the profits was being funneled to Gyeongmudae (the presidential residence, now the site of the Presidential Office). These allegations were never conclusively established but became the subject of considerable public discussion.

Despite the controversy, General Kim continued to confiscate shipments of pollack and use them to improve rations for his troops.

Kim subsequently requested that Gyeongmudae conduct a thorough investigation into the incident, and the dispute between the two generals was ultimately brought before the presidential office.

In the end, President Syngman Rhee removed both General Kim Seok-won and Chief of Staff Chae Byeong-deok from their respective posts.

However, after public attention to the Pollack Incident gradually faded, President Rhee reappointed Chae as Chief of Staff of the ROK Army on April 10, 1950—only eight months after his dismissal.

By contrast, General Kim Seok-won was never restored to active duty and remained in the reserve.

In retrospect, historians have offered differing assessments of these personnel decisions, particularly in light of the fact that North Korea launched its surprise invasion of South Korea just two months later.

4. Defense Minister Shin Sung-mo and Controversial Leadership

Defense Minister Shin Sung-mo frequently advocated a hard-line policy toward North Korea and publicly called for the unification of the Korean Peninsula through a northward advance. Nevertheless, he has also been criticized for failing to ensure adequate military preparedness before the outbreak of the Korean War.

According to historical accounts, shortly before the war began, Shin summoned not only division-level commanders but also several frontline commanders to an officers' club for a social gathering involving drinking. Around the same period, the government also disbanded approximately 20,000 members of the Homeland Defense Corps, which had served as a reserve force, and established the Youth National Defense Corps in its place. Critics have argued that this decision was driven more by political considerations than by military necessity.

When North Korea launched its full-scale invasion at 4:00 a.m. on Sunday, June 25, 1950, Army Chief of Staff Chae Byeong-deok attempted to contact Defense Minister Shin by telephone at his official residence but was unable to reach him. Chae then called Lieutenant Colonel Shin Dong-woo, the minister's chief secretary, at Gahoe-dong to inquire about Shin's whereabouts. According to historical accounts, Shin Dong-woo replied:

"The Minister is probably at his residence. However, as you know, he lived in Britain for many years, so on Sundays he does not meet with anyone or answer telephone calls."

During a cabinet meeting held at 4:00 a.m. on June 27, Shin reportedly stated that he was unaware of the current military situation before quietly leaving Seoul. Some retired senior officers later recalled that he played only a limited role in understanding or directing military operations during the critical early stages of the war.

For these reasons, Shin Sung-mo is frequently mentioned in discussions of civilian control of the military in South Korea. Critics of civilian control sometimes cite his tenure as an example of its potential failure. Supporters, on the other hand, argue that while civilian control is an essential principle of democratic governance, Shin's case demonstrates the importance of establishing institutional safeguards to ensure that individuals lacking the necessary qualifications are not placed in charge of national defense.

Meanwhile, spearheaded by Soviet-built T-34 tanks, the North Korean People's Army advanced rapidly. Seoul fell only three days after the outbreak of the war, forcing the ROK Army into a continued retreat toward the south. Amid this rapidly deteriorating situation, Army Chief of Staff Chae Byeong-deok found himself carrying an increasingly heavy sense of responsibility.

5. Inadequate War Preparedness

When the Korean War broke out in June 1950, the Republic of Korea (ROK) Army was inadequately prepared in several important respects.

The army suffered from a severe shortage of tanks and anti-tank weapons, and its forward defensive positions were not fully developed.

In addition, many senior commanders were away from the front because of weekend schedules, further complicating the military's initial response to the invasion.

Launching a surprise attack before dawn, the North Korean People's Army advanced rapidly behind Soviet-built T-34 tanks. The ROK Army lacked effective means to stop the armored offensive.

As a result, Seoul fell only three days after the outbreak of the war.

6. The Final Days of Chae Byeong-deok

After relieving Chae Byeong-deok of his position as Chief of Staff, Defense Minister Shin Sung-mo appointed him commander of the Yeongnam Regional Organization Command and sent him the following letter:

"You bear great responsibility for the loss of Seoul. You must atone to the nation and its people through your death. Take the lead and personally command your troops."

**Shin Sung-mo, Minister of National Defense**

Despite its imposing title, the Yeongnam Regional Organization Command had very few troops under its actual control. At the time, Chae commanded only about one hundred hastily assembled personnel gathered from the Masan and Busan areas. According to historical accounts, he interpreted the letter as an order to go to the front lines and fight until death.

Burdened by a profound sense of responsibility, Chae led his men to the front on July 24, 1950. By then, the North Korean People's Army was advancing into the Yeongnam region through the Honam area with overwhelming numerical superiority. Chae took command of a small force from the 15th Infantry Regiment of the newly organized 5th Infantry Division and moved toward Hadong in South Gyeongsang Province, near the border with Honam.

At 11:00 p.m. on July 27, Army Headquarters issued Operational Order No. 72, directing an attack against a North Korean battalion advancing toward Hadong with armored vehicles. Chae joined the operation with his troops alongside the U.S. Army's 19th Infantry Regiment under the command of Colonel Moore. During the ensuing Battle of Hadong on July 27, Chae was killed in action.

According to historical accounts, earlier that day Chae had assisted civilians fleeing the fighting before moving to Hadong Pass to observe enemy movements. While conducting reconnaissance, he was struck by a sniper's bullet that passed through his jaw and died at the scene.

Captain Kim Young-hyeok later testified that, because Chae's aide-de-camp, Lieutenant Lee Sang-guk, and several other officers were away at the time, he alone carried Chae's body approximately 20 meters to a U.S. military vehicle, after which it was transported to Jinju. The official biography of Chae Byeong-deok published by the Ministry of National Defense likewise states that he died instantly at the scene without leaving any final words.

Following his death, the South Korean government officially recognized Chae as having been killed in action, posthumously promoted him to the rank of lieutenant general, and awarded him the Eulji Order of Military Merit.

7. Conclusion

One of the principal reasons the Republic of Korea (ROK) Army was unable to respond effectively during the initial stages of the Korean War was the failure of its senior military leadership in personnel decisions and the inadequate level of war preparedness.

While North Korea, with extensive Soviet assistance, had carefully prepared for a full-scale conventional war centered on tanks and artillery, the ROK military leadership became overly confident after repeated successes in border skirmishes and consequently underestimated the combat capability of the North Korean People's Army. As a result, the country's defensive posture gradually weakened, and serious shortcomings in the command structure became evident once the war began.

In particular, many historians have argued that insufficient emphasis was placed on military competence and wartime leadership when making key personnel appointments. These shortcomings in leadership and command decisions are widely regarded as factors that contributed to the scale of the ROK Army's early defeats.

Ultimately, Seoul fell only three days after the outbreak of the war, and the Republic of Korea faced an existential crisis that threatened the very survival of the nation.