Because of the differing military technologies, both the Unitited States and North Vietnam believed that they would win and kept their aspiations high. Many years of war were required to discover which of these parties had drawn the right conclusion (which was North Vietnam).
Ambiguity about relative power is one of the conditions that encourage conflict.
Many wars have been fought to produce an image of power and being ready to use it. The American involvement in the Vietnam War is a good example.
Vietnam had no strategic importance to the United States, but American officials were concerned about the challenge to their country's image posed by the communist guerrilla movement there. They feared that the United States would be seen as weak-willed if it did not fight this movement, inviting communist aggression in other parts of the globe. This was part of a broader belief in interlocking commitments summarized in the statement, "If we aren't willing to fight them anywhere, we will have to fight them everywhere."
Concern about image threats is part of the structural change model.
One way to see the Vietnam War is to see is as a contender-defender episode embedded in a broader conflict spiral, the Cold War. The reason for this is that the United States during the Cold War was fighting communism, and the Vietnam War was only part of this escalation.