If asked why they were there, many would say simply "Somebody's got to give the Hun a bloody good kicking". It was what they were told! It was exactly the same on the other side too.

How do you know that Don?
How can you accuse those dead young men of believing shit because they were told to?

Hastings was not there, but historians use sources.
The IWM has thousands of ordinary soldiers' war diaries and letters.

He says,"Most veterans rejected the 'poets' view'. One old soldier, named Henry Mellersh, declared in 1978 that he wholeheartedly rejected the notion that the war was 'one vast, useless, futile tragedy, worthy to be remembered only as a pitiable mistake'.
Instead, wrote Mellersh: 'I and my like entered the war expecting an heroic adventure and believing implicitly in the rightness of our cause; we ended greatly disillusioned as to the nature of the adventure, but still believing that our cause was right and we had not fought in vain.'

That view was far more widely held by Mellersh's contemporaries than the 'futility' vision of Owen, Sassoon and their kin."