There is a distinction between believing something and having a set opinion. We talk about concrete setting, and that is the metaphor involved.

I note that you ignore the distinction I made between the things about which academic historians can reasonably expected to have some special expertise, such as about the facts of what happened, and the area where they do not, speculation about what might have happened but didn't.

The assertion that there was "no choice" for Britain but to wage war falls squarely into the latter category. (Unless it is a statement about the psychology of the decision makers, so that being the people they were there was no possibility that they could have acted otherwise, seeing them as some kind of automatons...)

If Alan Clark actually said that "The wartime generals were all cowards and incompetents " I would think it likely that that would have been overegging the pudding. I suspect that an examination of his book would indicate that to be an oversimplification of what he actually wrote. But the crucial issue in any case is not whether they were cowards and incompetents but rather that they made significant mistakes that caused the deaths of enormous numbers of their soldiers.

There seems to be a suggestion that the view that the war should be seen as a disaster rather than a success that vindicated the decision to wage it, and the manner in which it was waged means that the heroism and dedication of the soldiers is disregarded. That is untrue and extremely offensive. At any rate that seems the view of Michael Gove. I am not assuming that Keith is guilty of such a gross distortion.