The various civilized nations of the world went about killing each other with a new and frightening efficiency. The various armies were equipped with cloth caps and the front of the battle in Western Europe stagnated and the men were standing around in trenches all day.
Meticulous records were kept of casualties and people noticed that an awful lot of head wounds were being recorded. It was considered after a while wise to issue the men with helmets and so they were.
You would think that that would help but something extraordinary happened: it was noticed that almost immediately the number of men recorded with head wounds went up fivefold.
Now, why do you think that should be? Some people get it straight away other people just don't get it at all.
People who understood statistics a bit better were able to point out what actually was going on and the men were allowed to keep their helmets.
Spoiler : The Answer :
Spoiler : Did you get it? :Spoiler : Really? :Spoiler : Don't give up, have faith in yourself! :Spoiler : Ok, last warning. :It was to do with statistics and the way people were listed in the hospitals. You see what used to happen was a shell would land, short throw a load of clods of Earth into the air, and these would rain down from a very great height onto people and kill them. Those men would be listed as dead but instead after helmets were issued then they would land on the men and injure them they would then be listed as head wounds and that's why there was a sudden massive increase in the number of head wounds recorded in the hospitals.