The Communist surprise attack on South Korea was an indicator that the Cold War would be more serious than some had supposed.
President Harry Truman saw the Communist aggression not only as the occasion for a U.S. response in Korea, but also as the occasion to review U.S. preparedness worldwide, and make adjustments to defense policy as needed. Historians Allan Millett and Peter Maslowski write:
Much to the surprise of the Truman administration, the North Korean People’s Army (NKPA) crossed the 38th Parallel on June 25, 1950, and opened a three-year war for control of the Korean peninsula. The Korean War brought a major shift in United States military policy, for it provided an atmosphere of crisis that allowed the nation to mobilize for one war in Asia and rearm to deter another war in Europe. By the time the conflict ended in an uneasy armistice in July 1953, the United States had tripled the size of its armed forces and quadrupled its defense budget. It had also redefined the Communist threat to a challenge of global proportions.
As the reality emerged that the Communist threat was more than regional, President Truman assigned four objectives, not so much to the military broadly, but rather more specifically to the Army: to maintain and support a field army in Korea; to maintain and support one in Europe for the anticipated WWIII; to collaborate with the Air Force on a continental air defense system; and to maintain a strategic reserve should it be needed elsewhere on the planet.
These four tasks proved to be massive. The simultaneous effort to address all four of these goals stretched the Army thin. Historian William Donnelly writes:
The President and the Congress, however, did not provide the Army with sufficient resources to accomplish all four missions, and the service steadily deteriorated during these two years. The hurried expansion of the active force during the war’s first year, together with three decisions, created a serious manpower dilemma for the Army. These three decisions were: (1) to institute individual rotation in Korea; (2) not to hold draftees and mobilized reserve component personnel on active duty for the duration of the war; (3) to cut the Army’s budget but not its missions. The result was a constant shortfall of personnel, both in quantity and in quality, affecting combat effectiveness, operational readiness, training, and retention.
When the fighting in Korea began, the U.S. Army was adequately but not well prepared.
Because the war came as a surprise - unlike some other conflicts in the nation’s history - it is understandable that troop levels at the outbreak of hostilities were suboptimal. Historian Russell Weigley writes:
The troops in Japan were not well trained, partly because Japan offered so little ground for that purpose. Like nearly all American Army formations in early 1950, their units were understrength. Infantry regiments had only two battalions instead of the standard three, and artillery battalions had only two batteries instead of three. But the American troops were at least close by, and the Korean peninsula was accessible to air power vastly superior to anything the North Koreans could muster even without the atomic bomb, and to naval power which, though its ships were getting old and often had to be removed from mothballs to get into the fight, remained far and away the premier force of its kind on the globe.
American forces performed admirably in Korea, but the Army never reached a fully proficient presence there.
While one cannot write properly of ‘winning’ or ‘losing’ as the outcome of that conflict, it is objectively true that South Korea with its United Nations allies came very close to winning, and handily so. The lack of a South Korean victory was a negotiated and self-inflicted loss.
The U.S. Army performed admirably in Korea, but had to overcome handicaps to do so. Had the President Truman and the Congress allocated resources differently, a more proficient military would have given South Korea an even more dominating advantage.