A pillbox of the FW3/22 design, a regular hexagon, at Wellingore airfield, Lincolnshire. Some of the reinforcing steelwork can be seen, and another, identical pillbox is visible in the distance.

One of the principal designs of pillbox was the hexagonal FW3/22 infantry pillbox designed to accommodate up to five light machine-gunners (armed with Bren guns), together with one rifleman. It was to be built of reinforced concrete, with walls 12–15 inches thick, i.e. bulletproof. The huge loss of equipment in France, however, meant that the infantry rifle would have to replace the Bren in this and other designs. A larger design was numbered FW3/24; the most frequently built, this was an irregular hexagon, with a theoretical complement of five light machine gunners, two riflemen and a commander. FW3/23, a rectangular shape sometimes seen built into river or sea banks, had a rear portion accommodating an open light anti-aircraft position. Its complement was four men armed with three light machine guns and one rifle.

An FW3/28a pillbox with two alternative positions for a 2-pounder anti-tank gun above the Kennet and Avon Canal, part of the GHQ Line. Wootton Rivers, Wiltshire.

The design of even the standard FW3 pillboxes varied from area to area: for example, some entrances were protected by an external blast wall, which might also contain a loophole. In the absence of the blast wall, one assumes a wall of sandbags was constructed to protect an entrance, this vulnerable feature being positioned facing away from the likely direction of attack. One or more small rifle slits in the entrance wall gave rear protection. Other pillboxes, such as the FW3/27 often seen on airfields, where all-round fire was considered absolutely necessary, were entered by low-level ‘creeps’. Different Commands had their own designs: Northern Command, for example, employed a lozenge-shaped design, examples of which can be seen in the Holderness area of Yorkshire and along the River Coquet stop line. Inside the majority of pillboxes would be an internal wall, often ‘T’- or ‘Y’-shaped, to support the roof and deflect blast, splinters or bullets ricocheting inside the pillbox.

Where pillboxes were built in what were considered to be primary strategic locations, these were often of a so-called ‘shellproof standard’, having walls at least 42 inches thick, as opposed to the bulletproof standard of 12–15 inches. The shellproof design was expected to be proof against tank and light artillery fire. There is evidence that some pillboxes not built to this standard were later strengthened with additional concrete skirts. Along Southern Command’s section of the anti-tank GHQ Line, for example, in July 1940 it was planned to have approximately six hundred shellproof pillboxes in place, with a much smaller number of the bulletproof design of pillbox. In addition, over two hundred of the 2-pounder anti-tank gun design – the FW3/28 and FW3/28a (with dual positions for the gun) – were planned. Because of materials shortages and changes in tactical thinking, initial plans were seldom fulfilled.


The land defences of Britain 1940–2, showing principal stop lines (these often following physical features) and Army Commands.

The British Isles, located off the mainland of Europe, have faced the threat of large-scale invasions for almost a thousand years, the last successful landing being that of William of Normandy in 1066. William and his knights also brought over their horses (as the Wehrmacht, still partly dependent on horse-drawn transport, would have done in 1940). Medieval wars with France and Henry VIII’s conflict with Catholic Europe led to invasion fears and as a result a number of artillery forts were built along the south coast. The conflict with Napoleonic France led to the building of Martello towers (brick-built artillery towers sited to defend the vulnerable coastline of south-eastern England) from the end of the eighteenth century. The rise of the French navy under Napoleon III initiated the building of the powerful Palmerston forts around the main naval bases (named after the British Foreign Secretary) in the mid-nineteenth century. With the outbreak of the First World War and with German forces on the other side of the Channel, anti-invasion defences were constructed along British coasts. These included fieldworks, together with small concrete defence works; the latter were christened ‘pillboxes’ after their apparent resemblance to the small, round boxes used at that time to contain pills. Small reinforced concrete defence works had also been used with deadly effect by Germany, in conjunction with machine guns, along the Western Front.

The outbreak of the Second World War in September 1939 and the occupation of much of western Europe by Germany in the summer of 1940 meant that invasion was once again a likely threat. Even before the German offensive in France had ended, the British GHQ Home Forces had issued an instruction in the middle of May 1940 for defensive steps to be taken against the landing of enemy troops by air, tactics that had been employed successfully in Norway and Holland. With the fall of France in June, Germany began to make preparations for the invasion of Britain, issuing Führer Directive 16 on 16 July. If Germany had had sufficient maritime ability to invade at the time of the Dunkirk evacuation, then this might have met with success. However, she had also lost vital aircraft, especially transports, and much of the armoured equipment used in France was at its last gasp. Operation Sea Lion, the code name for the invasion, was planned to make use of both seaborne and airborne forces, and a date was set by Hitler and the German High Command for the launch of the operation: 16 September 1940. The planned invasion envisaged seaborne landings between Worthing and Folkestone with airborne landings behind the port of Dover.

A number of events led to the postponement of the planned invasion, the principal one being Germany’s failure to gain air superiority during the Battle of Britain. Another factor was the German navy’s (and probably also Hitler’s) disquiet at the chances of successful and sustained landings in the face of the much stronger Royal Navy, coupled with the prospect of deteriorating seasonal sea conditions. In addition, the attraction of an attack on Germany’s ideological enemy, the USSR, meant that in the late summer of 1940 Hitler had already begun to switch his attention eastwards, and the army groups gathered for Sea Lion were gradually moved to Poland. Hitler would pin his hopes on the success of the U-boat offensive and the Luftwaffe’s night bombing campaign against Britain, expecting that this would bring the country to its knees and lead to its surrender, or to the agreement of terms favourable to Germany, especially once the USSR was defeated. But this was not known to Britain in the latter part of 1940 and into 1941. Whilst Britain prepared for what seemed an imminent invasion, a part of the British Isles was already under German occupation: the Channel Islands had been seized in a relatively bloodless manner in June 1940; their occupation would last until May 1945.


The catastrophic collapse of the French Army and the British Expeditionary Force in the summer of 1940 led to the evacuation of British (and French) forces from Dunkirk, and this was coupled with the British Army’s massive loss of war material, especially heavier weaponry. The most serious losses were in heavy machine guns and artillery, especially anti-tank guns. The British Army’s 2-pounder anti-tank gun was a complicated and precision-made weapon and it would take time to make good the losses. In the meantime the Army would have to rely on extemporised anti-tank weapons such as obsolete artillery pieces and even the Molotov cocktail, a bottle filled with an inflammable liquid ignited by large matches attached to the sides of the bottle.

Hasty preparations were immediately put in hand for the country’s defence against invasion by sea and air: Britain now knew of Germany’s blitzkrieg tactics and could respond, albeit with very limited military assets. With Germany occupying most of western Europe, it was not known from which direction the enemy might come or where he might land. General Ironside, Commander-in-Chief Home Forces, had to produce a scheme to defend many hundreds of miles of coastline (the ‘coastal crust’), and to provide a substantial inland barrier (the GHQ Line), as well as mobile reserves behind the Line. In the event, the Germans would opt, in their planning for Sea Lion, for the shortest crossing route. The British Army Commands had also to consider a possible German occupation of the neutral Irish Republic with German diversionary attacks aimed at Ulster or, by air or sea, against the western side of Britain. Landings on the Scottish coast from occupied Norway had also to be considered.

The fear of fifth columnists and paratrooper landings led, on 14 May 1940, to the formation of the Local Defence Volunteers, soon to be renamed the Home Guard. A covert branch of the Home Guard was also formed, the Auxiliary Units, trained to function as stay-behind cells operating from underground, camouflaged bases. Their role would be to harass an invader’s rear areas by sabotage and assassination. In addition, a parallel secret intelligence organisation was set up with a force of civilian spies in order to gather intelligence information. This information was to be passed by radio to army signal units, who were also located in underground hides. The organisation was known as the Auxiliary Units Special Duties Section. Some remains may still be seen: for example, the camouflaged signals base (Zero Station) on the top of Blorenge hill above Abergavenny in South Wales. The National Trust organises guided walks at Coleshill House, the headquarters of the Auxiliary Units, where an underground training hide, known as an operational base, may still be seen.

The threat of enemy invasion, whether real or imagined, led to the erection of many improvised roadblocks around the country, intended to hinder enemy movement and to act as posts to check identities, but these often proved obstructive to the movement of home forces and many were soon removed. The enemy’s innovative use of aircraft to land troops in order to capture airfields and other strategic or vulnerable points such as bridges led to a new threat coming from the sky: airfields now had to be protected against airborne landings, as well as against bombing and strafing attack. Areas where enemy gliders or transport aircraft might land were obstructed by poles and wires, or whatever was available – even by old cars and sewer pipes. Lakes and reservoirs had cables stretched across their water, and pillboxes were sited to prevent enemy seaplanes landing and disgorging troops. The signal that enemy forces had landed was the ringing of church bells in the vicinity: church bells were otherwise not heard for most of the war.

Around and behind the coast, fieldworks and concrete defences (pillboxes and gun houses) were built, minefields were laid (in June 1940, fifty thousand anti-tank mines had been issued), and many types of obstacle were installed or erected to prevent the enemy’s movement, especially of his tanks. Twelve armoured trains, manned by Polish soldiers, patrolled the coast from Cornwall to the Moray Firth. The defence of beaches and landing grounds by pillboxes and fieldworks had begun before the Second World War in Britain’s colony of Malta, against the rise of Mussolini’s Italy.

In 1940 Defence Zones were established around the parts of Britain’s coasts deemed most vulnerable, with restricted access for civilians. Residents in the Zones were told to stay put in invasion occurred, to avoid roads being clogged with refugees, but this did not stop a gradual and large-scale migration from coastal areas in the early war years. Although a ‘scorched earth’ policy (the destruction of food supplies, petrol installations and vital public services and buildings so as to deny them to the enemy) was considered in the event of an invasion this idea was quickly dropped. To hinder an invader further, milestones and signposts were removed. Instructions were issued for the denial to an enemy of fuel supplies by immobilising machinery or by contamination. Also, any vehicles likely to fall into enemy hands were to be immobilised. Beaches were defended by pillboxes, barbed wire, minefields and, from 1941 onwards, anti-tank and anti-boat metal scaffolding.

Inland, anti-tank stop lines were built, the principal one being the GHQ Line running inland along the southern and eastern sides of England, protecting approaches to London, with subsidiary stop lines built by Army Commands to give some protection to the vital ports and manufacturing regions such as the Midlands against the invader’s armoured thrusts. These lines, a key factor of the country’s defences in the summer of 1940, followed existing features wherever possible, such as canals, railway lines, rivers and also natural barriers such as the North Downs (GHQ Line). Where existing features were not available, anti-tank ditches were dug. Crossing points were defended by pillboxes and gun houses, with major towns and cities along the lines’ routes turned into anti-tank islands. It was hoped that these defences would delay the enemy long enough for precious reserves to be directed towards the threat. In effect, a battleground had been prepared.

The British Expeditionary Force already had experience of building anti-tank ditches and pillboxes in France during the winter of 1939–40. The anti-tank ditches were revetted with wood to present a sheer face to any tank encountering the obstacle. Ideally, both faces of the ditch would be reinforced so as to prevent a tank backing out of the ditch. In other locations riverbanks were similarly revetted. Important bridges were identified for demolition, the larger ones receiving demolition chambers in bridge supports, such as the railway bridge crossing the South Forty Foot Drain in Lincolnshire. At Sarre in Kent minor bridges were destined to receive pipe mines. It was realised that not every bridge could be destroyed: vital services such as telephone or electricity cables, gas mains and water supplies often ran across bridges, meaning that these should not be destroyed. And the possibility of British counterattacks against the invader had to be considered. Roads, bridges and airfield runways would be cratered by buried charges – if time allowed.

Because the enemy’s intentions were not known, the defence posts along the lines had to have all-round defence. Where anti-tank obstacles of steel rails with concrete cylinders were sited, these had to be provided with hardened defences (pillboxes) or fieldworks for troops to prevent the obstacles’ removal. The surveying of the defence lines was carried out by Royal Engineer reconnaissance parties, sent by the Army Commands, which had previously identified suitable routes in their Command areas. It was intended that the lines and their defences would prove a barrier to the enemy’s general movement, especially that of his tanks and reconnaissance forces. Where the nature of the defence work was identified – be it pillbox, fieldworks, minefields or obstructed bridges – these would be marked on the ground and on a map referred to in the Royal Engineers’ report to the Command. Where bridges crossed the stop line, these were prepared for demolition, obstructed with steel rails or, where the surface of the bridge was suitable, mined. The anti-tank mine was a cheap and effective weapon. Large stocks were accumulated and used not only by the Army but also by the Home Guard: for example, Eastern Command (see the National Archives, reference WO 166/1193) anticipated that the Home Guard in the Cambridge area would acquire over ten thousand of these weapons by late 1941. The mines were not to be laid until the enemy was close.

The steel-rail anti-tank barriers were, on the giving of the appropriate code word (various words were used to denote different states of emergency), ‘armed’ by slotting them into wooden-lined prepared sockets, gravel being packed around any gaps to prevent removal by the enemy. Instructions issued by Northern Command in late 1941 advised that vertical and bent (not welded) rails presented a satisfactory anti-tank barrier as long as the sockets were also lined with wood. To reinforce the barrier, concrete cylinders (they came in two sizes), in groups of three, were to be placed in front of the steel barrier to prevent the tank charging and breaking the rails. In some areas the cylinders had a central hole in which to insert a pole to enable their movement along the ground. Gaps at the side of the barrier would be closed by concrete ‘dragons’ teeth’ (also known as pimples) or anti-tank walls. The inland stop lines, it was hoped, would prevent the rapid progress of the enemy’s reconnaissance forces and delay and ‘corral’ the enemy’s tank and infantry forces, giving time for the reserves to be gathered together for an attack. However, some of the stop-line defences were futile given the shallowness of many of the watercourses chosen, especially during the summer months. A Southern Command report in July 1940 on a proposed stop line along the River Wylye in Wiltshire concluded that it could be breached with ease and, once breached, would render the rest of the line ‘useless’. Although many stop lines were proposed, it is clear that a significant number were, on surveying, found to have no tactical value and were abandoned; others were never fully developed. In June 1940 Army Commands were also preparing towns and cities for defence as anti-tank islands, but at that time resources were very thinly spread. London, in addition to its southerly protection by the GHQ Line, would eventually have three concentric rings of defences, with the central government area of Whitehall being one of three ‘keeps’, the others being at Maida Vale and the Tower of London. The vital port of Liverpool, in addition to defences ringing the city, had also to have defences on the Wirral to protect the approaches to the Mersey Tunnel.

The pillboxes, designed to provide hardened fighting bases for the troops defending the stop lines and Vulnerable Points (VPs) such as airfields, were built in vast numbers in the space of a few summer months and were of a number of official and unofficial designs. Research carried out in connection with the Defence of Britain Project from 1995 onwards indicated that approximately 28,000 were built, of which a little short of 25 per cent survive. In May 1940, before France had fallen, a list of drawings was issued to Army Commands by the War Office Department FW3 (Fortifications and Works) of a range of pillbox designs for use in differing tactical situations. At the same time drawings were also issued for the design of the iron-rail anti-tank barriers, the bent-rail version (commonly known as the ‘hairpin’).



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