Pill Boxes on the Western Front

When the First World War froze into a static line of trenches stretching from the North Sea to the Swiss border, the most obvious means of protection against the murderous machine-gun fire which both sides inflicted upon each other was some form of shell-proof shelter which from which fire could be returned in safety, hence the development of the pill box. The idea was certainly not new but the technology required to build them under the prevailing circumstances presented problems hitherto undre