Site Visit Part II – Randalstown Forest, Second World War Defences

The pillbox is synonymous with the Second World War. Thousands were constructed across the United Kingdom (and Ireland1A programme of defence building was undertaken by the Irish along the River Boyne and around a number of south coast ports) to defend high-value areas or as part of a National defensive line. Many of them still remain and conjure up the romantic notion of local boys and men bearing arms to defend their country. Their modern interpretation is often the subject of much controversy with the context of their construction having been lost in the preceding 80 years. The area which is now Randalstown Forest has three pillboxes remaining, each with unique features, and the relationship between each one and where they sit in the landscape offering clues to help interpret them. In this article, I will attempt to place the pillboxes in the context of defending against invasion, and also look at each structure in turn to find clues about their construction and use.


The declaration of war in 19392Preparations for war had been undertaken during the preceding years including the development of new aircraft, research into early warning systems and civil contingent planning. saw an overnight change to the lives of citizens across Great Britain and Northern Ireland, but in these early days of the was there was little feeling that the population was in any great danger. It was another foreign war where the might of Great Britain and Her allies would prevail; even if the events of 1914-1918 were still very much present in everyone’s mind. I am sure there was dread at the thought of another generation of young men being sent to their fate, but in the early days at least the future didn’t look as bleak. However, the so-called Phoney War was soon to come to a bitter end. When the 390,000 strong British Expeditionary Force (BEF) was dispatched to France and Belgium in October 1939 they dug-in and waited for the war to begin. But for the next 7 months, there was little divisive action from either side. By May 1940 the heat was on and this vast force, along with French and Belgian counterparts, was engaged in the Battle for France. Within a month the BEF had been evacuated and the British Army had lost sufficient war-fighting equipment that they would almost certainly struggle to repel the German Army had they continued their push westward.

The first serious plans for the defence of Britain drawn up by General (later Field Marshall) Ironside, Commander-in-Chief Home Forces, relied on lines of continuous static defences, similar to those used (without great success I hasten to add) in France during the early days of the War. In 1940 a vast programme of construction was initiated comprising a thick ‘coastal crust’ of defences and a series of linear defences known as the General Headquarters (GHQ) line along the east coast of England. This was to be supplemented by smaller ‘stop lines’ across the country to hinder any advance if the Germans penetrated the GHQ line.

Northern Ireland received little attention in the early days, having been considered to be out of the reach of the invaders. Ironside, however, was concerned that neutral Ireland (and Northern Ireland by association) could be used to mount an invasion of England from the west. In the summer of 1940 reconnaissance of Northern Irish beaches was ordered.3British planning and preparations to resist invasion on land, September 1939 – September 1940. Newbold, David John, 1988

During the summer and autumn of 1940, counter-measures were taken to prepare a hot reception for the potential raider or invader. By means of concrete pillars, barbed wire and concealed firing points (…)

Chapter 5, the Threat of Invasion, Northern Ireland in the Second World War, John W. Blake, 1956 (reprinted 2000)

Ironside was succeeded late in 1940 by a Ulsterman; General Alan Brooke, who recognised the weakness of purely linear defensive lines and immediately halted Ironside’s plans. While the new plan incorporated much of the existing infrastructure, Brooke implemented a series of well-defended nodal points at natural junctions and focal points. Towns and villages became centres of resistance, while rivers and valleys became defensive features to channel any invaders towards the well-defended localities. This new plan combined the relatively flexible and inexpensive field defences with the more permanent hardened defences. These defences were independent of those constructed for the defence of specific areas such as factories, airfields or industrial areas.

An image of a house prepared for defence from the 1944 Field Service Pocket Book, Pamphlet No. 7, Field Engineering. In the event of invasion, strategic buildings around the nominated Nodal Points would likely have been defended in such a manner.

A demonstration by the Royal Berkshire Regiment from October 1941 shows what a roadblock may have looked like. It is likely that the approach roads to Randalstown would have been furnished with similar obstacles and defences. The large concrete blocks have been cast with corrugated iron as a mould. The square slots along the edge are for steel beams such as railway sleepers, so it is unusual that a rope has been used in their place; unlikely to be a deterrent to anything larger than a motorcycle as in this exercise. And as with all obstacles, they would have been overlooked by protected rifle and machine-gun positions.

Image right from the Imperial War Musem IWM H 14838.

Spotting a pillbox in the landscape today we often see red-brick clad bunkers sticking discretely above the landscape. This isn’t how they would have looked when concealed into the landscape. many techniques were used to hide the pillbox from view; both from the air and aerial reconnaissance and from passing patrols. One of the main principles employed in the camouflage of pillboxes was that of “merging with the background by elimination of shadows and the distortion of the silhouette.”4Military Training Pamphlet, No. 46, Camoflague, Part 2, Field Defences, 1941. Some examples of how a pillbox may have been merged are given in a 1941 pamphlet (left). Pillboxes were also disguised to great effect, especially in coastal towns or urban environments. There are some excellent images of camouflaged pillboxes on the Imperial War Museum archive.

Image left from Military Training Pamphlet, No. 46, Camoflague, Part 2, Field Defences, Figure, 12, dated 1941.

It’s also false to assume pillboxes were independent structures. Certainly, they formed a static stronghold in a defensive line, and they would likely have housed the more high-value weapons such as machine guns or anti-tank rifles. Other defences such as barbed wire entanglements, anti-tank blocks and ditches, and infantry trenches would have accompanied the pillbox in creating formidable defences. One type of defence that may well have been dug around these pillboxes in a 3-man weapon slit (right), the instructions for which were issued to troops in the Field Service Pocket Book.

Image right from Field Service Pocket Book Pamphlet, No. 7, Field Engineering, Figure 3, dated 1944.

A rare image of British soldiers defending a pillbox at Yarmouth during a training exercise. The pillbox can be seen in the background, with infantry trenches at the front and to the sides, as well as evidence that local vegetation has been stripped to aid fields of fire from the defensive positions. Further images in the series show barbed wire entanglements even further forward of the trenches. Copyright IWM H2701

By mid-June 19405Northern Ireland in the Second World War, John W. Blake, Chapter V: the Threat of Invasion, Section 2, footnotes there were up to 20,000 regular ground troops under the control of Headquarters Britsh Troops Northern Ireland (HQ BTNI). This was primarily 53rd (Welsh) Division responsible for Fermanagh, Armagh and South Down; 61st Infantry Division with responsibility for Antrim, Londonderry and Tyrone, including Belfast; and 148th Infantry Brigade Group. They were joined in early 1941 by 71st and 72nd Brigades and the entirety of 5th Division. Just as the threat of invasion was waning there were four divisions garrisoned in Northern Ireland as an anti-invasion force. The thought that the Germans would have been fought off by a hotch-potch Dad’s Army was incorrect.

Interpreting the Randalstown Pillboxes

A transport and industrial hub for over 200 years, Randalstown sees the congregation of roads from the north, east and west, as well as being located on the River Maine with its substantial railway viaduct. For any invading army to dominate this region, capturing Randalstown would be vital. The one set of natural obstacles preventing swift advance across the country we have an abundance of in Ireland; rivers. Many of which start or end in Lough Neagh and Randalstown is a mile from the shore.

As well as being prepared for defence as a Nodal Point, the bridges crossing the River Maine were had been prepared under a demolition scheme for destruction had the order been received. It is estimated that one Battalion of Infantry along with a Field Company of Royal Engineers could garrison a village for complete defence within 24 hours.6Royal Engineers Pocket Book, Chapter IV Defences, 1936. They would have required 800 long pickets, 1600 short pickets, 130 coils of barbed wire and three 3-ton trucks. Any enemy transit through Randalstown would be very difficult indeed.

Randalstown importance as a Nodal Point can be seen in this 4-inch to a mile Ordnance Survey map, the River Main (sic) cutting down the centre of the map.

With a huge programme of work undertaken in the spring and summer of 1940 at the direction of General Ironside, the three pillboxes outside Randalstown may have been constructed at this stage. It can only be assumed that they were surrounded by other field defences such as infantry trenches and barbed wire. I think it is unlikely that there was a continuous chain of pillboxes from Randalstown south to the shores of the lough along the river. Providing a formidable obstacle to any advancing troops attempting to move east across the country, these pillboxes with their light machine guns and mobile infantry would have had a great impact. They dominate this section of land, use the landscape to their advantage, and exploit the natural obstacle of the River Maine to their rear.

At the stage of the invasion where these pillboxes have entered the fight, it is likely that all bridges across the River Maine would have been intentionally destroyed. It is possible that these three pillboxes protected a crossing point to facilitate reinforcement or evacuation of troops to and from the frontline. Troop movement in and out of the area behind the pillboxes would have been covered from sight and direct fire. A small bridge does exist and can be seen to the bottom left of the image below. Information on the NI Historic Environment Map Viewer does not have this bridge listed as a prepared demolition site.

In the defence of a bridgehead over a river, the passage of which it is required to keep open with a view to a future advance, it will be necessary to locate troops in sufficient depth across the river to prevent enemy observed fire from being directed against the bridge.

The Infantry Division in Battle, Section 20, The Defensive Layout, 1950
An annotated aerial photograph from Google Earth. The image has been rotated to favour the main direction of fire from all three pillboxes. North is now to the right of the image and the top of the image is roughly west. Along the bottom of the image is the River Maine running north to south (right to left). Each ring, marked in yellow, is 500 yards in diameter; the effective range of the Enfield No. 4 rifle was up to 550 yards and for the Bren light machine-gun (LMG) anywhere from 600 yards to 1,100 yards depending on the firing position.

The three pillboxes sit almost exactly at the connection of the 500-yard rings, demonstrating that they have been sited very carefully so as to provide mutually supportive fire to each other, and can effectively deny freedom of movement to exposed enemy infantry anywhere within their range.

To achieve the greatest effectiveness of this position the pillboxes would have housed LMGs. The allocation of Bren Guns for an infantry division was anywhere upwards of 740 guns7WWII Equipment but after the losses of Dunkirk it’s not possible to know how many were initially deployed in Northern Ireland. By June 1940 it appears that there a total of 3,447 Brens available to the British Army.8WWII Equipment Ammunition does not appear to have been in short supply due to the rapid increase in war production.

(The Light Machine Gun) is the principal weapon of the infantry section and can be fired and maintained in action by one man. It can fire single rounds or produce automatic fire at a very high rate, if required, up to a normal effective range of 600 yards. When fired from a tripod this effective range may be considerably increased.

Infantry Training, Volume I, Pamphlet No. 6, The Light Machine Gun, 1948


The pillboxes at Randalstown are all of the same type; a variation on the Type 24 design of pillbox issued in May 1940.9Pillboxes of Britain and Ireland, Mike Osborne, 2008 (2012 reprint) They are of a hexagonal design with a longer rear wall to accommodate a full-height door and two smaller loopholes. There could be considered three front faces to the pillbox, each having a full-size loophole to direct the greatest volume of fire to the front arcs. Two final loopholes are in the flanking faces of the pillbox facing the rear flanks.

The Type 24 was one of the most common designs of pillbox constructed on Stop Lines in England, the majority of which had a central Y or X-shaped anti-ricochet wall designed to prevent bullets entering one loophole passing through the full pillbox and richoeting around the inside. None of the three Randalstown pillboxes have this feature. Many also had a blast wall covering the rear entrance providing some protection to the occupants from exploding shells to the rear.

There were two specifications of pillbox; bulletproof and shellproof. Bulletproof pillboxes (of which the variants at Randalstown are) had a wall thickness of between 30-40 centimetres and a concrete roof slab thickness of around 30cm. Shellproof pillboxes were twice the thickness with walls up to 130cm and were designed, as the name suggests, to resist shelling from field artillery. You can find out more about the thickness of protective materials required in my article Field Fortifications: ow thick was thick enough?

An annotated of a Type 24 pillbox showing the geometry. From the front (left image) there are three loopholes (A, B, C) providing frontal protection. Viewed from the side (right image) each flank is protected by a full sized loophole (D). Loophole C has been marked in both for reference. The rear of the pillbox is flat, parallel with the front face.

Shanes Park Pillbox

The defenders view. While the ground rises away from the pillbox, this would have allowed the defenders to remain unseen until any enemy crested the hill (Point A below) at which point they would likely be fired on. The tree line would not have been mature in 1940/41 and would likely have been cleared to present a clear field of fire.
A graphic representing the field of view from the pillbox set at 500 yards. Sitting at 36m above sea level, the pillbox would have been sitting in a dip, having to elevate to cover the road coming into their view at point A. This was the twelve o’clock position, or the central line of fire from the front loophole. Poor visibility to the rear of the position is acceptable due to the location of the river.

Randalstown Forest North Pillbox

The view isn’t much today, but without the trees, the vantage point on a ridgeline would have facilitated a large view and field of fire.
A graphic representing the field of view from the pillbox set at 500 yards. Sitting at 44m above sea level, this pillbox had the best field of view of all three. It is difficult to see now, but without the trees as they look in 2021, this box could have provided almost 360 degrees of protection, but the main field of fire was directed to the west (image left).

Protective Shutters

Looking through the metal debris on the floor it was possible to make out a number of the steel panels or shutters that would have reduced the aperture of the loopholes. An item that I haven’t seen before is also on the floor and this may have been an open frame used to fire through. As there are no supports internally for the tripod of bipod of a machine gun, this section may have helped give rudimentary support when the gun was firing.

Randalstown Forest South Pillbox

Now barely visible through the clearing in the artificially planted forest, the southern pillbox has been built in what is recorded as a rath; an ancient mounded enclosure.
A graphic representing the field of view from the pillbox set at 500 yards. Sitting at 31m above sea level, the southernmost of the three pillboxes would have been able to provide protection from the south.

Shelf Fixtures


This trio of pillboxes south of Randalstown has been a real pleasure to visit and research. They appear to sit in their original context within the landscape, which is rare. I am confident in my hypothesis that they were sited here to establish a bridgehead a protect a vital bridge crossing over the River Maine after all other bridges had been intentionally demolished and denied to the invaders. While mostly sitting as shells of their former being, tantalising clues remain about their fixtures and fittings; steel doors, internal steel shutters and wooden shelves. However, the intense planting of trees throughout the forest has likely destroyed any other field defences that may have been constructed.

All but one of these pillboxes can be visited on a visit to Randalstown Forest, and armed with a bit of this background information I am sure you can start to appreciate the landscape as it would have appeared in 1941 as the Nation prepared to defend until the end.

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  • 1
    A programme of defence building was undertaken by the Irish along the River Boyne and around a number of south coast ports
  • 2
    Preparations for war had been undertaken during the preceding years including the development of new aircraft, research into early warning systems and civil contingent planning.
  • 3
    British planning and preparations to resist invasion on land, September 1939 – September 1940. Newbold, David John, 1988
  • 4
    Military Training Pamphlet, No. 46, Camoflague, Part 2, Field Defences, 1941.
  • 5
    Northern Ireland in the Second World War, John W. Blake, Chapter V: the Threat of Invasion, Section 2, footnotes
  • 6
    Royal Engineers Pocket Book, Chapter IV Defences, 1936. They would have required 800 long pickets, 1600 short pickets, 130 coils of barbed wire and three 3-ton trucks.
  • 7
  • 8
  • 9
    Pillboxes of Britain and Ireland, Mike Osborne, 2008 (2012 reprint)