Warning: the photograph below is very graphic and may disturb some viewers, hence the spoiler tag. Click at your own risk.
The picture shows the skeletal corpse of a dead German infantryman (the helmet is clearly German) outside a dugout shelter. It has become fairly famous, and is featured in the opening credits of the classic BBC documentary series The Great War.
The fact that the body was left in situ long enough for the flesh to decay completely suggests to me that it may be from one of the most lengthy engagements on the Western Front - perhaps the Somme Campaign or the Battle of Verdun, either late in the battle or shortly after it ended, but this is just an informed guess.
Do we know who this man was, where and when the picture was taken, or anything else about it?