Here's a nice fact about WW1.
Apparently, when the war began, neither side issued helmets to their troops. They would walk around the trenches in their caps, or in the Germans' case, leather made Pickelhaubes.
Only around 1915 steel helmets were introduced, and there's quite a hilarious story about it. You see, by this time, the British generals realised a lot of their men were sent to hospital with head wounds, so they implemented the helmets. However, after the men were given these helmets, the number of men listed as 'wounded in the head' increased fivefold.
Incredibly enough, the generals thought the men were stupid, and began popping their heads over the parapets more often. Ergo, they pulled an order to remove the helmets.
Only a few smart people actually realised that the number of soldiers sent to hospital increased because they DIED LESS. The helmets deflected shrapnel, thus only hurting the user, rather than having him killed.