S4: How did the enemy exploit sustainment weaknesses to contribute to the US withdrawal to the Pusan Perimeter?

The NKPA was successful at exploiting two sustainment weaknesses at different levels of the US military:

1) Strategic/Theater: The US military overall- but in the Far East Theater specifically- saw a slackening of training, discipline, and equipment. After the conclusion of World War II the American public did not want nor expect a large conflict (nor expect one where grunts were involved) resulting in a hamstrung and severely limited ground force. This, coupled with the lax responsibilities of occupation forces in Japan, did much to diminish the average soldier’s competence. If there are not enough trained soldiers to fight then there definitely would not be enough to properly maintain and use what equipment had not been mothballed. In the end, the invasion of the South all the way to Pusan was met by continuous delaying actions IOT compensate for strategic/theater level maintenance and training deficiencies.

2) Tactical: The NKPA knew that the American forces would be reliant on secure supply channels and infrastructure to continue fighting. For a fighting force that was manned by experienced cadre and had a small logistical footprint such an enemy was easy to outmaneuver. Western armies were not prepared for the type of 360 degree warfare that communist armies had been perfecting and would rely heavily on their technological superiority in order to overcome their other shortfalls. No longer would the frontline be easily distinguishable with a (usually) secure rear with which to sustain an army.

The Pusan perimeter was a natural backstop for American forces because it played to the supply strengths of the US- proximity to Japan and a vast naval fleet- and to the main supply weakness of the NKPA- a logistics system that could not maintain itself over a large distance.