Logistics in the Battle of Pusan Perimeter (August 4 – September 15, 1950) during the Korean War played a decisive role in the battle. Efficient logistics, the management of personnel and materiel, supported United Nations (UN) supply lines while the North Koreans' routes of supply were steadily reduced and cut off. UN logistics improved throughout the Battle of Inchon and the defeat of the North Korean army at Busan.
UN forces, consisting mostly of troops from the Republic of Korea (ROK), the United States (US), and United Kingdom (UK), enjoyed overwhelming air and sea superiority during the battle. The UN efficiently procured and transported supplies from a large stockpile of materiel in nearby Japan.
In contrast, North Korean logistics were hampered by UN interdiction campaigns which slowed the flow of supplies from North Korea to the battle. Though supported logistically by the Soviet Union and China during the battle, North Koreans often had difficulties getting their supplies from depots to the front lines, leaving North Korean troops unsupported during several crucial engagements.
Background
Outbreak of war
On the night of June 25, 1950, ten divisions of North Korea's Korean People's Army (KPA) launched a full-scale invasion on the nation's neighbor to the south, the Republic of Korea. The force of 89,000 men moved in six columns, catching the Republic of Korea Army by surprise, resulting in a complete rout. The smaller South Korean army suffered from widespread lack of organization and equipment, and it was unprepared for war. Numerically superior, North Korean forces destroyed isolated resistance from the 38,000 South Korean soldiers on the front before it began moving steadily south. Most of South Korea's forces retreated in the face of the invasion. By June 28, the North Koreans had captured South Korea's capital of Seoul, forcing the government and its shattered army to retreat further south.
To prevent South Korea's complete collapse, the United Nations Security Council voted to send military forces. The United States' Seventh Fleet dispatched Task Force 77, led by the fleet carrier USS Valley Forge; the British Far East Fleet also dispatched several ships, including HMS Triumph, to provide air and naval support. Although the navies blockaded North Korea and launched aircraft to delay the North Korean forces, these efforts alone did not stop the North Korean Army juggernaut on its southern advance. To supplement the air support, US President Harry S. Truman ordered ground troops into the country. Although the Eighth United States Army's US 24th Infantry Division was in Japan and was available to respond to the situation, cuts in military spending after the end of World War II meant that the overall strength of the US military in the Far East was limited and the division itself was understrength and operating outmoded equipment. Nevertheless, the division was ordered into Korea.
The 24th Infantry Division was the first US unit sent into Korea with the mission to take the initial "shock" of North Korean advances alongside the South Korean army, delaying much larger North Korean units to buy time to allow UN reinforcements to arrive. The division was consequently alone for several weeks as it attempted to delay the North Koreans while the 7th Infantry Division, 25th Infantry Division, 1st Cavalry Division, and other Eighth Army supporting units moved into position. On July 5, during the first battle between American and North Korean forces, advance elements of the 24th Infantry Division were badly defeated at Osan. Over the course of the following month, the 24th Infantry Division was repeatedly defeated and forced south by the stronger and more heavily equipped North Koreans. During this time heavy fighting occurred around Chochiwon, Chonan, and Pyongtaek before the 24th Infantry Division made a final stand at Taejon. Although they were almost completely destroyed in the fighting, the US troops were able to delay North Korean advance until July 20, by which time the Pusan Perimeter had been established. With UN units arriving every day, the Eighth Army was able to build up a force of combat troops that were roughly equal to North Korean forces attacking the region.
North Korean advance
With Taejon captured, North Korean forces began the effort of surrounding the Pusan Perimeter from all sides in an attempt to envelop it. The North Korean 4th Infantry Division and the North Korean 6th Infantry Division advanced south in a wide coordinated maneuver that was aimed at the UN's left flank. Advancing on UN positions, they repeatedly forced US and South Korean forces to withdraw. Although they were steadily pushed back, South Korean forces increased their resistance further south in an effort to delay North Korean units as much as possible. North and South Korean units sparred for control of several cities, inflicting heavy casualties on one another. The Republic of Korea Army forces defended Yongdok fiercely before being forced back. They also performed well in the Battle of Andong, where they were successful in repelling North Korean advances.
In the west, US forces were pushed back repeatedly before finally halting the North Korean advance. Forces from the 3rd Battalion, 29th Infantry Regiment, newly arrived in the country, were wiped out at Hadong in a coordinated ambush by North Korean forces on July 27, leaving open a pass to the Busan area. Soon after, Chinju to the west was taken, pushing the 19th Infantry Regiment back and leaving routes to the Pusan open for North Korean forces. US units were subsequently able to defeat and push back the North Koreans on the flank in the Battle of the Notch on August 2. Suffering mounting losses, the North Korean 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 Pusan Perimeter.
United Nations logistics
On July 1, the US Far East Command directed the Eighth United States Army to assume responsibility for all logistical support of the United Nations Command (UNC) in Korea. This included the ROK Army, US Army and British Army forces operating in Korea. It also included support for the ships of Australia, Canada, New Zealand and the Netherlands which were also contributing to the effort. When the Eighth Army became operational in Korea, this logistical function was assumed by Eighth Army Rear which remained behind in Yokohama, Japan. This dual role of the Eighth Army—that of combat in Korea and of logistical support for all troops fighting there—led to the designation of that part of the army in Korea as Eighth United States Army in Korea. This situation existed until August 25. On that date the Far East Command activated the Japan Logistical Command with Major General Walter L. Weible in command. It took over the logistical duties previously held by Eighth Army Rear. It also assumed responsibility of the movement of refugees and prisoners of war.
The supplies needed to support the American and South Korean armies came through the United States and Japan. Whatever could be obtained from stocks in Japan or procured from Japanese manufacturers was obtained there. In early July 1950, Japanese manufacturers began making antitank mines and on July 18 a shipment of 3,000 of them arrived by boat at Busan. The equipment and ordnance supplies that was available to the United States forces in Korea in the first months of the war was largely due to the "roll-up" plan of the Far East Command which had been in effect for some time before the outbreak of hostilities. It called for the reclamation of ordnance items from World War II in the US Pacific island outposts and their repair or reconstruction in Japan. This plan had been conceived and started in 1948 by Brigadier General Urban Niblo, the senior Ordnance Officer of the Far East Command. During July and August 1950 an average of 4,000 automotive vehicles cleared through the ordnance repair shops each month; in the year after the outbreak of the Korean War more than 46,000 automotive vehicles were repaired or rebuilt in Japan.
Challenges
The re-equipping of the ROK Army presented the UN forces with a large logistical problem in July. To meet part of the requirements, the US command contracted Japanese manufacturers in August to produce 68,000 vehicles for the ROK Army, mostly cargo and dump trucks, with first deliveries to be made in September. However, the largest challenge faced by UN forces was a shortage of ammunition. At the outbreak of the war and up until the Pusan Perimeter engagements, the UNC's forces had to rely mainly upon the stock of World War II surplus ammunition. Much of this malfunctioned or no longer worked, indeed in some cases up to 60 percent did not work, and as a result ammunition, particularly for crew-served weapons, was frequently in short supply. From the outset, high-explosive anti-tank (HEAT) ammunition was particularly scarce, but this changed as US and Japanese manufacturers increased production to meet wartime needs, as a part of the Far East Command's "Operation Rebuild". By August 1950 this operation had assumed gigantic proportions and before the end of 1950 it had expanded to employ 19,908 people in eight Japanese shops. Through these efforts, UNC logistics situations improved over time, but nevertheless ammunition remained in short supply for much of the war.
Another issue that strained the UN logistics system was the lack of a previously drafted resupply plan. Consumption rates differed among the various units and as a result of a lack of coordination, some UN units faced supply shortages when other units would request more material than they actually needed. In order to rectify this situation UN logisticians were forced to hastily create a plan as the need arose.
The lack of armor available was also a serious issue of the UNC. In order to meet the demand, a variety of armored old platforms were hastily rebuilt and modified for movement into the Pusan Perimeter. M4A3 Sherman medium tanks (preferably the most advanced model, the M4A3E8 (76)W HVSS Sherman) from World War II were pulled from stocks and rebuilt for use in Korea. M15A1 Half-tracks were also rebuilt and modified for use in Korea. During early engagements, the M24 Chaffee light tank was the main armored vehicle used by the Americans because it was most readily available and most combat-ready; nevertheless, it performed poorly against heavier North Korean armor. All of these weapons had been used in World War II and were considered in poor condition. The appearance of the North Korean T-34 tanks forced the US to move large numbers of heavier, more powerful tanks into the battle. During August, six tank battalions, with around 69 tanks each, arrived at Pusan. By the end of the month there were more than 500 UN tanks assembled there. Most were M4A3E8 Shermans, and the bigger M26 Pershing heavy tanks, although a limited number of the new M46 Patton tanks were also moved into the perimeter.
On July 9, the US 2nd Infantry Division, with several armor and antiaircraft artillery units, was ordered to proceed to the Far East. The next day, MacArthur requested that the 2nd Division be brought to full war strength, if possible, without delaying its departure. He also reiterated his need of the units required to bring the four infantry divisions already in the Far East to full war strength. He detailed these as four heavy tank battalions, 12 heavy tank companies, 11 infantry battalions, 11 field artillery battalions, and four antiaircraft automatic weapons battalions per division. By August 7, the US 9th Infantry Regiment was operational in Korea, and had been sent to the Naktong Bulge area. However it would be the end of the month before the rest of the 2nd Infantry Division arrived in Korea.