By contrast, the U.S. military gave fewer resources to the occupation of Korea. It was clear that the Soviets, who occupied North Korea, constituted a danger. The Americans knew this; they saw the Soviets as a potential threat to South Korea. But U.S. intelligence underestimated how soon North Korea would be able to launch an attack on the South, and they underestimated the size and strength of the attack.
South Korea is officially the Republic of Korea (ROK), and North Korea is the Democratic People’s Republic of Korea (DPRK). The name of the DPRK is, of course, a fiction and a piece of propaganda: it is neither democratic, nor the will of the people, nor a republic; it is a dictatorship.
The U.S. understood that the Soviet-backed North was a threat, and for this reason, kept troops stationed in the ROK. The U.S. had a significant occupational force in South Korea in the immediate postwar months and into 1946. By 1950, because the U.S. military underestimated the speed with which the DPRK could build up a massive invasion force, the number of U.S. troops and ROK troops on hand was small and underequipped. In 1947, 1948, and 1949, the U.S. had steadily reduced the number of troops in South Korea. Along with this was a reduction in weapons and other equipment. Although the U.S. had indicated that it would help the ROK equip its own army, the process of arming the ROK was happening very slowly. The number of U.S. troops was approaching zero when the surprise invasion from the North began.
The United States had approximately 500 military officers in the ROK when the invasion started on June 25. In addition, there were a few USAF personnel on the ground as well. On June 27, Truman authorized Air Force and Navy actions, and on June 30 he authorized American ground troops. The first combat soldiers arrived on July 1.
When the DPRK began its large-scale surprise attack on the ROK in June 1950, the situation quickly became dire. Forces from the North conquered and occupied the vast majority of the South within a few weeks. ROK and U.S. forces were desperately defending a small piece of territory as the last remnant of democracy on the peninsula.
The defense of the ROK became officially a United Nations action in early July. Troops from Mexico, the Netherlands, France, the Philippines, Turkey, Thailand, South Africa, Greece, Belgium, Luxembourg, Ethiopia, and Columbia would eventually be part of the conflict. It is not only oversimplified, it is wrong to frame the Korean War as a United States endeavour. It was a United Nations endeavour.
Even after the arrival of U.S. combat troops, the situation continued to deteriorate. The DPRK’s army, called the Korean People’s Army (KPA or NKPA) continued to advance until late August and early September. British, Australian, Canadian, and New Zealand troops joined the American and ROK troops. The KPA cornered them in the southeast, where they defended the Pusan Perimeter, which held for several weeks.
The situation changed because Pusan received delivery of large amounts of men and equipment, because the U.S. opened a second front by invading Inchon on the peninsula’s western side, and because the KPA’s supply lines were overextended. Additionally, the Inchon invasion threatened those supply lines. The landings at Inchon came as a surprise to the KPA.
From the beginning, Truman worked to ensure that the action would be understood as a United Nations undertaking, as historians Allen Millett and Peter Maslowski write:
Within two weeks of the NKPA invasion — while the ROK fell back in disarray — the Truman administration established the international and domestic political foundation for an extended and substantial American military commitment to Korea. Of high importance was Truman’s determination to use the war as a test of the United Nations’ ability to meet aggression with collective military action. Assisted by Russia’s temporary absence from the Security Council, the United States guided several resolutions through the Security Council that gave the intervention United Nations sanction. The aim of UN action in July 1950 was to restore the prewar border and stop the war, either by negotiation or battlefield victory. In popular interpretation the war became an international “police action” rather than a national conflict. Nevertheless, Truman also requested and received overwhelming Congressional support for emergency, war-related measures: supplemental defense funds, draft extensions, reserve mobilization, and expanded presidential powers. Truman consulted with Congressional elders about the commitment of American ground troops and found them acquiescent. In the traumatic days of June 1950 the President might have received a formal declaration of war if he had so chosen, but he and his advisers regarded their actions as fully sanctioned by the United Nations charter. They also assumed the responsibility of fighting the war as part of a coalition whose ardor for the war waxed and waned outside American control.
The U.S. military leadership was inclined to see the situation through the lens of the war in the Pacific, concluded only five years earlier. This view had advantages and disadvantages. The benefit was that it allowed the officers to employ lessons learned from earlier experience. The drawback was that the UN coalition was looser than the WW2 allies had been, in the sense that the individual members weren’t necessarily absolutely committed; another drawback was that the Korean conflict, while a total war for the ROK and the PDRK, was not necessarily a total war for the UN coalition members, and the coalition certainly wasn’t insisting on an unconditional surrender as the only acceptable resolution. For these reasons, it was not practical or possible to transfer wholesale the WW2 strategic and tactical templates onto the situation in Korea.
Like the Pacific war, air and sea power were essential supports for the action on land, as Russell Weigley writes:
American naval power and the peninsular configuration of Korea for a time gave the war, from the American perspective, a heartening similarity to the Pacific war of 1941-45. The Army units thrown into Korea from Japan suffered severe initial defeats, and by late some it was touch and go whether the Americans and South Koreans could retain a foothold on the peninsula around the port of Pusan. But even the initial defeats could be regarded with the consoling reflection that America had suffered similar defeats in the Pacific not long before and had quickly recovered, while the pattern of recovery in Korea became discernable even as the defeats continued. It was air and sea power that assured against complete ejection from Korea. Together the Air Force and the Navy carried enough group troop reinforcements to the Naktong River line around Pusan to begin to equalize and then to turn the numerical balance of combat effectives against the North Koreans. Meanwhile, as long as numbers remained inadequate and combat skills and weaponry on the ground deficient, the Air Force and the Navy added enough fighting power to hold the Naktong line. The Navy anchored the flank on the Sea of Japan with offshore bombardment, and the Air Force and Navy planes gave tactical support all along the line.
For the U.S., the Korean conflict was one of several concerns to be managed. President Truman also needed to keep a full army in Europe, ready to respond at any time to a Soviet attack, and he needed to have a credible continental air defense system over the 48 United States. And, of course, he needed to have reserves for any unexpected events which might happen anywhere around the globe. So Korea couldn’t be a total war for the United States.
This divided military attention was codified in a document titled NSC 68. This National Security Council paper set the direction for much of America’s Cold War activity, and was kept classified for twenty-five years.
In addition to divided military attention, budgetary concerns also prevented the U.S. effort in Korea from being an all-out effort. The American public did not view Korea as they had viewed WW2. They weren’t ready for rationing, war bond drives, and the militarization of the civilian economic and industrial base. The political leadership in Washington was aware that there was a limit to the amount of sacrifice which the public would make for the Korean conflict, as William Donnelly writes:
In the crisis atmosphere created when the People’s Republic of China entered the Korean War in late 1950, President Truman approved a large increase in the Fiscal Year 1952 military budget to achieve by 1952 the forces previously planned to be ready by 1954. Following Eighth Army’s defeat of the Chinese spring 1951 offensives and the start of armistice negotiations in July 1951, the crisis atmosphere began to wane. Concern in the executive and legislative branches over damaging the economy by excessive military spending began to reassert itself, but did not prevent President Truman from approving in August 1951 a Joint Chiefs of Staff recommendation to increase the active force structure. The Army’s share of this increase included two infantry divisions and one armored division and 68,000 more personnel. The increase in divisions was driven by the needs of NSC 68. The infantry divisions were to replace two others from the General Reserve which had deployed to Japan after the four divisions there were deployed to Korea, and the armored division was to go to Germany. The increase in personnel was to cover both the new units and the demands of operations in Korea.
The Korean War began, therefore, with a massive retreat of ROK forces. The war came very close to ending, and the ROK came very close to being entirely destroyed, within its first few weeks. It would have been a swift and devastating loss. The reinforcement of Pusan and the landings at Inchon happened in the nick of time.
The war got off to a bad start for the ROK because U.S. military presence in the ROK was nearly non-existent in June 1950, because U.S. military intelligence underestimated the strength of the KPA and the KPA’s Soviet support, because intelligence didn’t discover how quickly the invasion from the North would be launched, and because the U.S. military had other pressing global tasks. In addition, the U.S. political establishment and the U.S. voters were not eager to take on the significant financial and social pressures of keeping forces in the ROK prior to June 1950, or of maintaining a large war effort in the years after June 1950.