A historian can and will describe events, as they happened and what effect they had on the future, suggesting the past as reason.

Hastings can do that and does.

He also commentates on the social setting, impact and rationale. That is using his historian credibility to put a particular slant on things. Professionally known as a hack.

The threat was real. The ensuing carnage was tangibly real. The drift into war for all sides was inevitable.

But the reason for war was incompetence and jingoism from all sides. Hence the war to end wars was a sop to the men to justify their slaughter, and that was wrong. Pushing men over the top to try and swamp the opposite trenches was dereliction of duty to their men. Men died through awful decisions.

You seem to propose that reminding ourselves of this shows disrespect to the dead? Kidding ourselves that war is just, that parochial interests are paramount to the effect of killing your people to achieve it. THAT is disrespect of the dead.

Lest we forget? Lest we forget why it shouldn't happen again, not lest we forget how brave the poor buggers were.