We have just seen Sir Peter Jackson's film They Shall Not Grow Old.
It is brilliant, very disturbing, deeply moving. It explains why my grandfather never mentioned it.
My own father fought in Africa so missed the trenches.
Any man or woman intent on war, fighting or even hating their fellows should see this film, they should see the expressions on the faces of the young teenage boys - both German and Allied who have just been through a battle, the trenches lined with filth, rats, lice and battered bodies and you will know it just is not worth it.
And this is not Hollywood, this was real.