Final answer:
The US failed to win a swift victory against North Korea due to difficulties with strategy and terrain, as well as the focus on Europe rather than Asia.
Step-by-step explanation:
The US failed to win a swift victory against North Korea right at the beginning for several reasons. One reason was that they had difficulties with strategy and the terrain.
North Korea had the advantage of being supplied with Soviet tanks and other technically advanced equipment, while the US was hesitant to provide similar aid to South Korea. Additionally, most US leaders were focused more heavily on Europe than Asia at the time.