Pillbox Reinforcement and Improvements (British Home Defence)

Another fascinating post from DaveT

Considering that the second posting on the article that I submitted to Think Defence – “The Changing Fortunes of Pillboxes” – is still generating some comments I thought I would offer this post. It is the draft of a page soon to be posted on my website, hopefully before the end of the month. It looks in more detail at the aspect of pillbox reinforcement outlined in my previous posts.

During 1940 the defences built against invasion were intended to “hold up enemy forces landed by sea or air” They were also designed to “meet the weapons which the enemy is most likely to bring”.

GHQ considered it unlikely that defences in Britain would have to be able to withstand the deployment of heavy guns as was the case on the Continent. Such guns would almost certainly be tractor drawn equipment. This type of equipment would unlikely be available to parachute troops or airborne troops. Neither would they be likely mounted in light or medium tanks, which would probably be the first to be landed by sea.

Many pillboxes were only bullet proof as this was considered sufficient to withstand most of the weapons likely to be deployed against them during the initial stages of invasion.

However it was recognised that if pillboxes had to withstand a deliberate and determined attack, the worst case should be planned for and pillboxes should be designed to withstand all modern weapons.  As early as August 1940 the question of pillbox reinforcement was raised.  The minutes of a conference on Defence Policy, Eastern Command noted that key pillboxes were to be 3’6” thick, the remainder 15”. The minutes also note “Where 15” pillboxes are to be brought up to 3’6”, only those sides which are liable to attack by gunfire need be strengthend.”

By 1941 GHQ had became concerned that pillboxes were obviously not proof against high velocity anti-tank weapons. A Research Board carried out trials on reinforced concrete that would be required to stop a 6 ponder shot. The Board also felt confident in calculating the requirements needed to stop the German 88mm.

A pillbox capable of stopping such weapons would need to be likely 6- ft thick. Existing pillboxes could also be strengthened to a degree.

This work has been carried out on this Type 24 Pillbox, RAF Bawdsey, Suffolk

It was recognized that such work would require a huge amount of labour and materials, both in short supply. It would not be possible to carry out such work in all Commands simultaneously so it was recommended that priority be given to Southern and Eastern Commands on vulnerable areas. The Chief Engineer GHQ recommended that the following level of protection should be provided:

(a)    Protection in the walls to meet an attack by an 88mm gun at 500 yards allowing for the impact of six shots in a 6-ft square.

(b)    Protection in the roof to withstand a 250 kilo bomb.

First priority to be given this level of protection was anti-tank gun pillboxes with L.A emplacements to be second priority.

As a result of the recommendations, the Commander in Chief directed that first priority would be given to anti-tank gun pillboxes on beaches in the specially vulnerable areas of Dungeness, Dover to Ramsgate in Southern Command and Southwold in Eastern Command. Both Southern and Eastern Command were asked to review their requirements in this matter and to submit proposals for improvement of pillbox defences. This could either be new pillboxes or strengthening existing ones. The following details were to be provided:

(a)    Serial No

(b)    Location

(c)    Outline plan and elevation of existing pillbox, including loopholes and requirements of new arcs of fire if required.

(d)    For new pillboxes, an outline plan, type of loophole required and arcs of fire. Walls should be 6-ft thick.

Designs were to be provided by GHQ and no modification of these plans would be permissible. GHQ emphasised that this was a long term programme with no prospect of completing even a very limited number in the immediate future.

Eastern Command noted that there were no anti-tank gun pillboxes in the Southwold area but submitted details of nine existing pillboxes in Southwold, one at Dunwich and one at Minsmere to be strengthened and a new pillbox to be constructed at Walberswick. It is likely this work was never carried out – the only surviving pillbox today on this list is the one at Dunwich which certainly has not been strengthened.

As well as reinforcement, GHQ recommend a further improvement to pillboxes in 1941 – “In general, opportunity should be taken to eliminate many of the redundant loopholes with which the earlier types of pillboxes were “riddled”. What may be called the “sieve” type of pillbox is nothing but a death trap”.  In Suffolk, 54th Div drew up a list of 127 pillboxes in which some loopholes were to be blocked.

A Suffolk Square which has had a Turnbull mount added for a light machine gun and also some of the embrasures blocked.

GHQ considered an alternative to concrete works which would be capable of withstanding determined attack  – a small steel machine gun post distributed in depth similar to the Hobbs casemate constructed during the last year of the Great War.  The Hobbs Casemate was basically a steel cupola mounted over a 3ft 9 in pit with only 18in showing above ground level.  Hobbs’ design was a result of his experience in 1917 against machine guns in fortified positions. The rationale for this was the age old problem of gun and armour – the gun would always win in the end.

Even the Maginot type of fortification was not impregnable.

These small posts were inconspicuous, easily hidden and were bullet and splinter proof. It would be hard for a tank to hit except at short range. GHQ noted that a number of similar designs existed at the War Office and were worthy of further trial. They would require less steel per weapon to be protected than reinforced pillboxes. They were designed to fit into a system of field defences. Presumably the Tett Turret and Allan Williams Turret were examples of these designs. The idea was never really taken up as so few of these structures were constructed.

A WW1 German machine gun post, Bourlon Wood, on the Siegfried II Stellung (or to the British the second defensive system of the Hindenburg Line known as the Marcoing Line). This is possibly the type of pillbox that influenced Hobbs (although in this case it is a concrete cupola mounted over a concrete lined pit).

The design for the Tett Turret was a rotating steel turret mounted onto a sunken concrete pipe but the only known examples (including one at Sudbury, Suffolk – now destroyed) actually had concrete turrets. It could incorporate two rifle men or a Bren gunner and his number two. It was primarily designed to defend road junctions, its lower profile than a pillbox being its main selling point. It proved too cramped and it was argued a slit trench would provide similar protection so only a handful was ever constructed.

A sketch showing the design of the Tett Turret

The Allan Williams Turret consisted of a steel cupola mounted over a sunken pit. It could be rotated through 360° and had mounts for Bren and Lewis light machine guns and the Boys anti-tank rifle. Of the 199 ordered 11 Corps, Eastern Command, received 116.

AW Turret





Pillboxes, TNA

Pillboxes – A Study of U.K Defences 1940, H Wills, Leo Cooper, 1985

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November 11, 2011 5:04 pm


I was once told that all personnel and wheelbarrows involved in the construction of pillboxes had to keep to duckboards to avoid leaving muddy trails that would be visible from the air. A slight additional complication!

Gareth Jones
Gareth Jones
November 11, 2011 5:56 pm

@ Another excellent post Dave T!

Gareth Jones
Gareth Jones
November 14, 2011 12:47 am

@ Dave T – I’ve been thinking about the belief you mention that no heavy guns would be in the initial invasion forces; what about the 75mm infantry guns and early mark IV tanks with the same(?) Weapon? IIRC these were designed to deal with machine gun nests and fortified positions.

There was also the Recoiless rifles of the Paratroopers, but they may not have been issued until later.

Gareth Jones
Gareth Jones
November 14, 2011 1:33 am

Modern version of the Tett turret?


Gareth Jones
Gareth Jones
November 14, 2011 1:58 am

smaller version with just ATGW; don’t think it can be lowered like the larger version above:


Interesting article about Soviet/Russian prefabricated ground structures:


November 14, 2011 12:24 pm

hi Gareth, It was certainly expected that tanks would be landed in the early stage of invasion. The initial attack was expected to be by parachutists/airborne troops to seize aerodromes/ports followed by landing craft containing troops/light tanks. Perhaps I did not make it clear enough in the post that key pillboxes and many on stop lines were constructed to 3’6″ thick and considered shell proof. However it was the German 88mm that caused the most havoc with fortifications in France and it was such modern high velocity weapons that GHQ became concerned about in 1941.

Gareth Jones
Gareth Jones
November 14, 2011 2:19 pm

@ Dave – thank you for the clarification. Just me getting the wrong end of the stick.