I agree. The critical fact in this instance is that the vast majority of Americans were willing to put up with the war in Vietnam as long as it didn't grow. Speculating about an alternative America where this wasn't the case requires us to make up many, many facts, that would significantly reduce the believability about any conclusions we draw.

That's why historians discourage speculation - because it reduces the legitimacy of the field and the value of its conclusions.

> Under that logic we may as well never study history

I would love to understand why you think my statement implies this.

I think it's particularly interesting given that I have a degree in history, with a specialization in US National Security Policy in the 20th century, so I don't think I generally give people the impression that "we may as well never study history," especially the history of the Vietnam War. In general, the reviews I receive are quite to the contrary.