The U.S. exited World War II believing that strength would win every war. How did events in the 1960s not support this idea?
I think that the Vietnam Conflict would be the single point to demonstrate that the United States' feeling of invincibility to emerge after the Cold War was forever punctured. There were so many elements to support this destruction of invincibility that the Vietnam War might be seen as the singular event to suggest that so much of American confidence had been dissipated in large part due to the conflict. The American forces were simply not adequately prepared for what confronted them in Vietnam. The physical conditions, the war-fighting strategies of the opposition, even being able to clearly demarcate who was "friend" or "foe," and the mere reasons why the opposition was fighting were all elements that the United States either misread or simply failed to acknowledge. The North Vietnamese featured a sense of resilience and defiance that was completely misunderstood and misread by the Johnson Administration, while the South Vietnamese government's corruption was something that baffled members of the administration. The sense of understanding and paradigm that the United States had when it entered the decade was completely absent when it exited it and Vietnam had much to do with that transformation.