Concrete Pillboxes were first built by the Germans in WWI and quickly copied by the Allies. The Pillbox models include some of the standard designs which were built by the British in WWII. This includes the impressive Type 28a Gun Emplacement.
Pillboxes which are typically built into defensive lines but have always been susceptible to modern weapons. However, until fire support is able to disable the pillbox, they are highly effective at slowing down an enemies advance and potentially stopping the advance in its tracks.
Pillboxes were built such their fields of fire overlapped and where possible, their field of fire was such that, each pillbox could support the other.
Pillboxes are still used today and can be found guarding entrances to military bases, high value targets and roadblocks