A TRUTH about war that brings you up with a jolt is that, within a generation or so of any war ending, its causes are a mystery to the young.

This applies even to the two world wars, which run like chasms across the 20th century. How many people who came through the second could give an account of the origins of the first? How many who came through both could say what the Boer War was about? Or the Crimea?

Considering how any war dominates all else while it is happening, and how major wars cast strong shadows for decades, the speed with which the reasons why a war was fought, and why so many died, sinks into oblivion is truly amazing.

Even remembrance of "the glorious dead'' has a cut-off point. "We remember the dead of the two world wars and later conflicts'' are the words routinely intoned against pictures of Remembrance Day ceremonies. Why don't we remember the dead of all our wars?

But what we need more than longer retrospective remembrance is anticipated remembrance. Poppies would be worn and wreaths laid for today's children, or those yet unborn, who are destined to die serving in future conflicts. For conflicts there will be. And deaths there will be. Yet those who stood at the first Remembrance Day ceremonies in 1919 imagined that their dead had at least been sacrificed in a "war to end all wars''.

"Remembrance'' should come with guilt. Our collective conscience needs to be pricked. So a forward-looking remembrance ceremony would include these lines by Cecil Day Lewis:

Will it be so as before -

Peace, with no heart or mind to ensure it,

Guttering down to war

Like a libertine to his grave? We should not be surprised.

And this by Thomas Hardy - God addressing the dead in a country churchyard, shaken in their coffins by gunnery practice - incidentally before the First World War:

The world is as it used to be:

All nations striving strong to make

Red war yet redder. Mad as hatters

They do no more for Christ's sake

Than you who are helpless in such matters.

The great First World War poet Siegfried Sassoon, who served in the trenches, abhorred the Menin Gate, the great arch inscribed with the names of 55,000 missing British dead from the Ypres battlefields. Deeply moving, the nightly sounding of The Last Post that still takes place there might seem to expose a colossal misjudgement by Sassoon. Certainly no one would endorse his description of the gate as "this sepulchre of crime''.

And yet was Sassoon really wrong? Every Remembrance Day ceremony that takes place against a backdrop of continuing war is at best a betrayal of those who died, at worst a mockery of them. Early in the Second World War Sassoon wrote:

I hear an aeoplane

what years ahead

Who knows? -

but if from that machine should fall

The first bacterial bomb, this world might find

That all the aspirations of the dead

Had been betrayed and blotted out...

More than 60 Remembrance Days later, that prospect is closer than ever.