No the design of pill boxes goes way further back than that. Pill Boxes were used in the Boer War, some even being two story. I'm sad enough to have a couple of books specifically about them.
The WW2 ones were often very much adapted to local conditions and what was available by way of materials. Several on the Kent and Sussex coastal strip were cast in concrete using the same reusable form work.
The WW2 ones were often very much adapted to local conditions and what was available by way of materials. Several on the Kent and Sussex coastal strip were cast in concrete using the same reusable form work.