Pill Boxes on the Western Front - front cover
Title:  Pill Boxes on the Western Front
Author: Peter Oldham
Publisher:  Pen and Sword Publishing
ISBN:  978-1-84884-439-1
'A guide to the design, construction and use of concrete Pill Boxes, 1914-1918'

This is the new paperback edition of a book originally published back in 1995.  The author had a career as a concrete technologist, and maybe no surprise therefore that he took an interest in the development of Pill Boxes as we came to call them, or MEBUs as the Germans referred to them (Mannschafts-Eisen-Beton-Unterstand = reinforced concrete shelter for troops to stand under).
I suspect that many like myself will often associate the concrete Pill Box with those we see here in Britain that date from WW2, or those of the German Atlantic Wall, and the Siegfried and Maginot lines.  In fact there were huge numbers used in WW1, and some of those that survive today could well be mistaken by the casual visitor as something from WW2.  Although we think of the static Trench Warfare of the years of WW1, it was originally seen as a war of movement, one which didn't happen, and we didn't pay too much attention to fixed defence positions at first.  It was the German army that first took best advantage of using concrete shelters for their troops, to protect them against artillery and machine gun fire.  Once the British and French realised how effective they were, both as troop shelters and machine gun posiitions, so we investigated those we did capture, and began building more of our own.  As the war progressed, so the technology of the designs, and the protection they offered, was improved.
Peter Oldham has written a really interesting and readable book about their development during the course of the war, one might say their evolution.  Building work in the front line attracted attention and invited attack, so camouflage and simpler construction methods, such as pre-cast sections or building them from blocks were all widely used.  Only further back could large scale concrete construction go ahead unhindered.  Then as the lines did move after an offensive, captured pill boxes would be 'converted' by the new owners, often being reversed as doors usually faced away from thee enemy, so once captured needed to be sealed and a new entry opened in the opposite side.
The book is well illustrated thoughout, with sketches of the different types of construction, cross-sections showing how they were made up, period photos along with many photos from recent years showing the remains of those that can still be found today, though they are still disappearing on a regular basis as they deteriorate or are demolished to make way for new construction.  It is broken down into 7 chapters, covering Development, the early work and evolution of the cement, then Solid Defence as Germany started constructing permanent defences and how geological services and materials supply became established by both sides.  Then the British Findings as they studied what they captured on the Somme, and mention of studies and reports, a couple of which are reproduced as appendices in the book.  Then the Difficult Conditions encountered in construction, and the use of pre-cast blocks.  The External and Internal issues are dealt with, such as camouflage outside and the comfort and safety of those inside, as well as the work involved in turning a bunker around.  Towards the end, major works in the Defence Lines are tackled, before a final section on Coastal Defences both here in the UK and on the Belgian Coast by the Germans.  These are all followed by a useful Gazetteer, describing where a number of remaining concrete pill boxes from WW1 may still be found.
As someone who has gained an interest in bunkers and pill boxes over the years, or 'lumps of old concrete' as my family refer to them as, this is a fascinating read about the early days of the military use of concrete and steel reinforments, and the changes in design to meet different objectives.  Should it just be able to withstand small arms fire, or the impact of artillery rounds, as depending on that answer, different issues are involved in their design.  As technology moved on during the war, so too did the technology behind the structure of reinforced concrete defences and this is a good insight into those early days.
For details of this and other books by Pen and Sword, do check their website.