My old dad (whose father fought in the Great War) would bang on about the fraternisation in the trenches. He was disgusted at the very idea, and used to say one should make up one's mind - are we at war with these people or not? If so, one can hardly treat them as mates for a few hours, Christmas or not. Every individual combatant has a family and a mum who loves him. But collectively they are a killing machine. Kill or be killed.