The Battle of the Pusan Perimeter, known in Korean as the Battle of the Naktong River Defense Line (Korean: 낙동강 방어선 전투), was a large-scale battle between United Nations Command (UN) and North Korean forces lasting from August 4 to September 18, 1950. It was one of the first major engagements of the Korean War. An army of 140,000 UN troops, having been pushed south to the brink of defeat, were rallied to make a final stand against the invading Korean People's Army (KPA), 98,000 men strong.
UN forces, having been repeatedly defeated by the advancing KPA, were forced back to the "Pusan Perimeter", a 140-mile (230 km) defense line around an area on the southeastern tip of South Korea that included the port of Busan (then spelled Pusan). The UN troops, consisting mostly of forces from the Republic of Korea Army (ROKA), United States, and United Kingdom, mounted a last stand around the perimeter, fighting off repeated KPA attacks for six weeks as they were engaged around the cities of Taegu, Masan, and Pohang and the Naktong River. The massive KPA assaults were unsuccessful in forcing the UN troops back farther from the perimeter, despite two major pushes in August and September.
North Korean troops, hampered by supply shortages and massive losses, continually staged attacks on UN forces in an attempt to penetrate the perimeter and collapse the line. The UN forces, however, used the port to amass an overwhelming advantage in troops, equipment, and logistics, and its navy and air forces remained unchallenged by the KPA during the fight. After six weeks, the KPA force collapsed and retreated in defeat after the UN force launched a counterattack at Inchon on September 15, and the UN forces in the perimeter broke out the following day. The battle was the farthest the KPA would advance in the war, as subsequent fighting ground the war into a stalemate.
Background
Outbreak of war
Following the outbreak of the Korean War, the United Nations decided to commit troops in support of South Korea, which had been invaded by the neighboring North Korea. The United States subsequently sent ground forces to the Korean Peninsula with the goal of fighting back the North Korean invasion and to prevent South Korea from collapsing. However, US forces in the Far East had been steadily decreasing since the end of World War II, five years earlier, and at the time the closest forces were the 24th Infantry Division of the Eighth United States Army, which was headquartered in Japan. The division was understrength, and most of its equipment was antiquated due to reductions in military spending. Regardless, the 24th Infantry Division was ordered into South Korea.
The KPA, 89,000 men strong, had advanced into South Korea in six columns, catching the ROKA by surprise and completely routing it. The smaller ROKA suffered from widespread lack of organization and equipment, and was unprepared for war. Numerically superior, KPA forces destroyed isolated resistance from the 38,000 ROK soldiers on the front before moving steadily south. Most of South Korea's forces retreated in the face of the advance. By June 28, the KPA had captured South Korea's capital Seoul, forcing the government and its shattered forces to retreat further south. Though it was steadily pushed back, ROKA forces increased their resistance farther south, hoping to delay KPA units as much as possible. North and South Korean units sparred for control of several cities, inflicting heavy casualties on one another. The ROKA defended Yeongdeok fiercely before being forced back, and managed to repel KPA forces in the Battle of Andong.
Outnumbered and under-equipped US forces—committed in piecemeal fashion as rapidly as they could be deployed—were repeatedly defeated and pushed south. The 24th Division, the first US division committed, took heavy losses in the Battle of Taejon in mid-July, which they were driven from after heavy fighting. Elements of the 3rd Battalion, 29th Infantry Regiment, newly arrived in the country, were wiped out at Hadong in a coordinated ambush by KPA forces on July 27, leaving open a pass to the Busan area. Soon after, Chinju to the west was taken, pushing back the 19th Infantry Regiment and leaving open routes to Busan. US units were able to defeat and push back the KPA on the flank in the Battle of the Notch on August 2. Suffering mounting losses, the KPA force on the west flank withdrew for several days to re-equip and receive reinforcements. This granted both sides several days of reprieve to prepare for the attack on the Busan Perimeter.
Prelude
Forces involved
The KPA was organized into a mechanized combined arms force of ten divisions, originally numbering some 90,000 well-trained and well-equipped troops in July, with hundreds of T-34 tanks. However, defensive actions by US and ROK forces had delayed the KPA significantly in their invasion of South Korea, costing them 58,000 of their troops and a large number of tanks. In order to recoup these losses, the KPA had to rely on less-experienced replacements and conscripts, many of whom had been taken from the conquered regions of South Korea. During the course of the battle, the KPA raised a total of 13 infantry divisions and one armored division to fight at the Pusan Perimeter.
The UN forces were organized under the command of the Eighth United States Army, which served and was headquartered at Taegu. Under it were three weak US divisions; the 24th Infantry Division was brought to the country early in July, while the 1st Cavalry Division and 25th Infantry Division arrived between July 14 and 18. These forces occupied the western segment of the perimeter, along the Naktong River. The ROKA, a force of 58,000, was organized into two corps and five divisions; from east to west, I Corps controlled the 8th Infantry Division and Capital Divisions, while II Corps controlled the 1st Infantry Division and 6th Infantry Division. A reconstituted ROKA 3rd Infantry Division was placed under direct ROKA control. Morale among the UN units was low due to the large number of defeats incurred to that point in the war. US forces had suffered over 6,000 casualties over the past month, while the ROKA had lost an estimated 70,000.
Troop numbers for each side have been difficult to estimate. The KPA had around 70,000 combat troops committed to the Pusan Perimeter on August 5, with most of its divisions far understrength. It likely had less than 3,000 personnel in mechanized units, and around 40 T-34 tanks at the front, due to extensive losses so far in the war. UN commander General Douglas MacArthur reported 141,808 UN troops in Korea on August 4, of which 47,000 were in US ground combat units and 45,000 in ROKA combat units. Thus, the UN ground combat force outnumbered the KPA 92,000 to 70,000. UN forces had complete control of the air and sea throughout the fight as well, and US Air Force and US Navy elements provided support for the ground units throughout the battle virtually unopposed.
Overall command of the naval force was taken by the US Seventh Fleet, and the bulk of the naval power provided was also from the US. The United Kingdom also provided a small naval task force including an aircraft carrier and several cruisers. Eventually, Australia, Canada, the Netherlands, and New Zealand provided ships as well. Several hundred fighter-bombers of the Fifth Air Force were positioned within the perimeter and in Japan, and just off the coast were US Navy aircraft aboard the USS Valley Forge and the USS Philippine Sea. By the end of the battle the Eighth Army had more air support than General Omar Bradley's Twelfth United States Army Group in Europe during World War II.
From south to northeast, the KPA units positioned opposite the UN units were the 83rd Motorized Regiment of the 105th Armored Division and then the 6th, 4th, 3rd, 2nd, 15th, 1st, 13th, 8th, 12th, and 5th divisions and the 766th Independent Infantry Regiment.
Throughout September 1950, as the battle raged, more UN forces arrived from the US and other locations. The 2nd Infantry Division, 5th Regimental Combat Team, 1st Provisional Marine Brigade, and British 27th Commonwealth Brigade arrived in Busan later in the fighting, along with large numbers of fresh troops and equipment, including over 500 tanks. By the end of the battle, Eighth Army's force had gone from three under-strength, under-prepared divisions to four formations that were well-equipped and ready for war.
Logistics
UN logistics
On July 1, the US Far East Command directed the Eighth Army to assume responsibility for all logistical support of the US and UN forces in Korea, including the ROKA. Support for the American and South Korean armies came through the United States and Japan. The re-equipping of the ROKA presented the UN forces with major logistical problems in July. The biggest challenge was a shortage of ammunition. Though logistics situations improved over time, ammunition was short for much of the war. Consumption of supplies differed among the various units and a lack of a previously drafted plan forced UN logisticians to create a system on the fly.
The majority of resupply by sea was conducted by cargo ships of the US Army and US Navy. The massive demand for ships forced the UN to charter private ships and bring ships out of the reserve fleet to increase the number of military vessels in service. Busan was the only port in South Korea that had dock facilities large enough to handle a sizable amount of cargo. An emergency airlift of critically needed items began almost immediately from the United States to Japan. Although it did not fly into Korea, the Military Air Transport Service (MATS), Pacific Division, expanded rapidly after the outbreak of the war. The consumption of aviation gasoline thanks to both combat and transport aircraft was so great in the early phase of the war, taxing the very limited supply available in the Far East, that it became one of the serious logistical problems. From Busan a good railroad system built by the Japanese extended northward. The railroads were the backbone of the UN transportation system in Korea. The 20,000 mi (32,000 km) of Korean vehicular roads were all of a secondary nature, as measured by American or European standards.
North Korean logistics
The North Koreans relied on a logistical system which was very lean and substantially smaller than the UN system. This logistics network was therefore capable of moving far fewer supplies, and this caused considerable difficulty for front-line troops. Based on the efficient Soviet Army model, this ground-based network relied primarily on railroads to transport supplies to the front, while troops transported those items to the individual units on foot, trucks, or carts. This second effort, though more versatile, was also a substantial disadvantage because it was less efficient and often too slow to follow the moving front-line units.
North Korea's lack of large airstrips and aircraft meant it conducted only minimal air resupply, mostly critical items being imported from China. Other than this, however, aircraft played almost no role in North Korean logistics. The North Koreans were also unable to effectively use sea transport. Ports in Wonsan and Hungnam could be used for the transport of some troops and supplies, but they remained far too underdeveloped to support any large-scale logistical movements, and the port of Inchon in the south was difficult to navigate with large numbers of ships.
In mid-July, the UN Far East Air Force Bomber Command began a steady and increasing campaign against strategic North Korean logistics targets. The first of these targets was Wonsan on the southeast coast of North Korea. Wonsan was important as a communications center that linked Vladivostok, Siberia, with North Korea by rail and sea. From it, rail lines ran to all the KPA build-up centers. The great bulk of Russian supplies for North Korea in the early part of the war came in at Wonsan, and from the beginning it was considered a major military target. By July 27, the FEAF Bomber Command had a comprehensive rail interdiction plan ready. This plan sought to cut the flow of KPA troops and materiel from North Korea to the combat area. Two cut points, the Pyongyang railroad bridge and marshaling yards and the Hamhung bridge and Hamhung and Wonsan marshaling yards, would almost completely sever North Korea's rail logistics network. Destruction of the rail bridges over the Han River near Seoul would cut rail communication to the Busan Perimeter area. On August 4, FEAF began B-29 interdiction attacks against all key bridges north of the 37th Parallel in Korea and, on August 15, light bombers and fighter-bombers joined in the interdiction campaign.
The supremacy of the Fifth Air Force in the skies over Korea forced the North Koreans in the first month of the war to resort to night movement of supplies to the battle area. They relied primarily on railroads to move supplies to the front, however a shortage of trucks posed the most serious problem of getting supplies from the trains to individual units, forcing them to rely on carts and pack animals. The KPA was able to maintain transport to its front lines over long lines of communications despite heavy and constant air attacks. The UN air effort failed to completely halt military rail transport. Ammunition and motor fuel, which took precedence over all other types of supply, continued to arrive at the front, though in smaller amounts than before. At best there were rations for only one or two meals a day. Most units had to live at least partially off the South Korean populace, scavenging for food and supplies at night. By September 1 the food situation was so bad in the KPA at the front that most of the soldiers showed a loss of stamina with resulting impaired combat effectiveness.