Stoplines: Some tactical notes

After Dunkirk (4/6/40) there was an obvious and urgent requirement to put the country into a state of defence as quickly as possible, and the result was the construction of stoplines.

Stoplines are usually broken down into three categories:

a. Coastal fortifications,

b. The G.H.Q. Line, and

c. Secondary stoplines

These notes refer to the last two categories only.

The order to construct the stoplines must have been given by Field Marshall Ironside, CinC Home Forces from 23rd May 1940, though the actual text of the order has not yet come to light. It must have been signed around 4/6/40, probably rather hastily as Longmate (1)comments that pillbox construction was proceeding before he had worked out his strategy.

Once stopline construction had been ordered things moved remarkably quickly. The basic thinking was spelled out in a Southern Command memo dated 22/6/40 (2) on the construction of G.H.Q. zones, which stated: “The immediate object is divide England into several small fields surrounded by a hedge of anti-tank obstacles which is also strong defensively, using natural accidents of the ground where possible. Should A.F.V.s or airborne attacks break into the enclosures the policy will be to close the gate by blocking the crossing over the obstacle and let in the ‘dogs’ in the shape of armoured formations, or other troops, to round the cattle.”

And again, in a letter to 1st Canadian Division on the same subject, “The general idea is to provide a series of anti-tank obstacles which can be used to confine and isolate an A.F.V. attack from any direction. These A.T. obstacles will therefore capable of being defended from either direction.”(2)

These communications plainly show that the stoplines were to block the progress of armoured columns, setting them up for a counter-attack. A stopline would a continuous anti-tank obstacle, natural if possible, covered by pillboxes and other prepared positions.

An interesting and important item (3) dated 27/6/40 proposes the construction of a stopline to defend Birmingham from the south. The proposed line runs from the Severn east to Watling Street, i.e. the junctions with Western and Northern Commands. To its north, i.e. behind it, are proposed nine anti-tank islands.

This memo shows how the concept of defence-in-depth was already appearing, and that stoplines would inevitably face in a specific direction. It is not too surprising to note that on 1/7/40 the Commander of Salisbury Plain produced a memo(2) registering his disapproval of the purely linear stopline concept: “If a determined attack were made upon it by enemy tanks they would undoubtedly penetrate somewhere and create a gap which would render the remainder of the line useless.”

A few few days later, on 9/7/40 a V Corps Operational Order, No 3 (2) decreed that on stoplines “Main crossings, usually in towns, must be preserved for the use of our own troops in the forward areas. Such crossings will be defended by putting them, or ie towns or villages containing them, into a system of all-round defence.” These instructions also conceded that defensive posts may be pillboxes if really necessary, but they must be concealed and be behind the anti-tank obstacle. If, owing to the lie of the land, it was absolutely necessary to place such a post on enemy side of the obstacle then it must be tank-proofed (easier said than done!) These instructions clearly show that the weak points of the purely linear scheme were quickly realised.

Actually, at the time there must have been some considerable misunderstanding as to what the stoplines were for, as indicated by a memo (4) dated 26/7/40 from 3 Division enquiring whether Stopline Green was a stopline only or a defensive psition covering Bristol. The difference may rest in arcane 1940s military terminology.

On 27/8/40 a memo (5) (all memos are Southern Command unless otherwise stated) stated that the Home Guard would hold a portion of the stoplines but as there are not enough of them the villages on the stoplines must be organised for all-round defence.

On 19/9/40 a memo (4) on the deployment of 4 Corps in the G.H.Q. Reserve noted at there were now two armoured divisions, only lightly armed, ready to operate against the flanks of the advancing Germans. It may be suspected that the vulnerability of the flanks of a Panzer division might have been exaggerated, but at least the importance of motorised infantry was fully appreciated.

On 28/10/40 a report (6) recommended that the anti-tank ditch between the Taunton Stopline anti-tank islands should be covered by anti-tank guns and on 6/10/40 (6) the Taunton Stopline is mentioned as including twelve anti-tank islands.

On 7/7/41 a Staff College Precis (7) noted that stoplines were constructed in depth to hinder A.F.V.s, in most cases they were not manned, but may be manned by Home Guards. By this time the Germans had invaded Russia (22/6/41) and the threat of invasion had become insignificant. Finally, on 6/10/41 the Southern Command was mentioned (8) as having abandoned the stopline principle in favour of a policy of holding centres of resistance.

The Development Of Main Material Components

Before considering the changes chronicled above it is worth a glance at the development of the main material components of the stoplines: the anti-tank ditch and the pillbox.

Pre-War manuals (9) describe an anti-tank ditch as being 8ft wide and 3ft deep, triangular in cross-section, the side closest to the enemy being a long sloping ramp running down to a near-vertical face. The spoil would be banked up on the enemy’s side to lengthen the ramp. This cross-section was replaced by a rectangular one 5ft deep (10) and, in May 1941 (8) by an isosceles triangle, 9ft deep. The improvement was not obvious.

The roll of pillboxes changed dramatically. Initially they were weapons positions rather like stationary tanks, but soon they came to be recognised as death-traps if used tike that and troops were instructed to use them only as shelters from artillery fire and to rush outside to fight (again, easier to say than do!).

These changes, which occurred very rapidly, in the design of the anti-tank ditch and role of the pillbox generate the feeling that insufficient planning was put in before construction was started, and the changes must have had some influence on the whale stopline concept.

As has been shown, the stoptine concept lasted a very short time, roughly six months saw it go from a continuously defended anti-tank obstacle to a series of anti tank islands. In view of the effort and expense involved in stopline construction, and that their obsolescence was not forced by warfare, it might be felt that their construction (at least in their original form) was a mistake. It may beconstructive to consider their origin, and there are two aspects of this:

1. Tactical concepts

2. Perceived threat.

1. The basic statement of tactics will be found in the Field Service
Regulations, and in the 1935 Edition it is written (p.137): “The foremost
position will consist of a belt of defended locations with intervals between
them, arranged in depth and affording each other mutual support.” This seems a reasonably common-sense approach.

On the subject of protection against A.F.V.s (p.82) it is stated: ‘Positive means of defence include the use of natural obstacles (such as woods, streams, marshy ground), of the protection afforded by buildings (or by blockhouses specially built where time is available), and the construction of road blocks or artificial obstacles of various types.” This is starting to look like a stopline, but it is still far form being a continuous line.

At this period and anti-tank defence must inevitably have been based on the anti-tank gun, heroic Home Guard expedients notwithstanding (1) and no realistic exercises could be held to try out defences as the R.A. did not have an anti-tank battery until 1938 (12). Consequently this section in the F.S.R.s would have been rather visionary, but it is unfortunate that anti-tank defence was moved out of the context of general field fortification.

Defensive tactics do not seem to have been studied to any depth between the World Wars. Various semi-official textbooks (13) almost ignore the subject, which is peculiar in view of the success of German field defences during the Great war, which were based on deep defensive zones and counter-attack units: a kind of prepared battlefield concept (14). More particularly, the lack of interest in anti-tank defence is amazing in view of the heat generated by arguments about tanks.

2. The perceived threat was the tank. Not only does the Staff College Precis say so but the nature of the stoplines shows it. No doubt a stopline would have brought to a halt a column of light tanks or armoured cars hurtling along with no reconnaissance or air cover, but the Panzer divisions were not like that. They contained infantry, artillery and engineer units, operatedon a rather more sophisticated level and showed many times in Belgium, France and Russia that they could crush defences like the stoplines quite easily.

It may be conjectured that some tank enthusiasts, who wrote between the Wars that future mobile operations would be carried out by large numbers of small armoured columns, were actually believed, and the stoplines were built against that threat (15). If this is so, and taking into account Liddel-Hart’s enthusiasm for the light tank, stopline design seems more sensible. The threat, unfortunately, was wrongly perceived: the Germans preferred to keep their armour concentrated, as the Eighth Army was to find to its cost.

In conclusion, the original stopline design appears to have been a mistake, and could be put down to a misconception of the threat. But on another level it may have seemed that there was no alternative. Any form of defence in depth pre-supposes the availability of forces for counter-attack. In the months following Dunkirk such forces simply were not in evidence.

As they became available the stoplines faded away.

Calling stoplines into existence cost vast amounts of money and inconvenience, and delayed training of regular troops. But their existence allowed more confidence to be placed in the Home Guard, which meant more troops being freed from static guard duties and being available for real training. At least one author claims that this factor was crucial to D-Day planning (16). Also, of course, the stoplines, along with all other fortification, would have had a certain deterrent effect on the Germans’ invasion planning and a heartening effect on civilian morale, a continuous line more so than a series of anti-tank islands (10). At the end of the day, it would be rash to either criticise or praise the construction of the stoplines.

(All P.R.O. documents are at Kew)

1. Island Fortress by Norman Longmate

2. P.R.O. WO 199/1800

3. P.R.O. WO 199/1800/20.

The proposed stopline would run from the Severn (junction with Western Command) at Upper Arley, three milesnorth of Bewley, down-river to the Droitwich Canal then overland to the R. Avon at Binton, four miles west of Stratford. Then along the Avon to
Leamington and along the railway line and R. Swift to Watling Street (Northern Command) two miles west of Luttersworth. The anti-tank islands named are Redditch, Hemley in Arden, Kidderminster, Stratford-on-Avon, Warwick/Leamington, Coventry, Northampton, Kettering and
Worcester. The last is not actually north of the line but on it. Certainly on the map it is the key to the whole area.

4. P.R.O. WO 199/1704

5. P.R.O. WO 199/1801

6. P.R.O. WO 199/1810

7. P.R.O. WO 199/567

8. P.R.O. WO 199/1735

9. The Manual of Field Engineering, Vol 1, 1933, amended 1938

10. See our Bristol Outer Defences in Loopholes 4 &5 for the anti-tank ditchand the reaction of Mr Powell and his family on finding that they would be behind it.

11. For sceptical comments on Molotov cocktails etc see the Tank in Spain
by Maj. Gen. J.F.C. Fuller, Army Ordnance July/August 1938

12. History of the Royal Regiment of Artillery, Between the Wars by Maj. Gen. B.P. Hughes

13. Examples of these being Historical Illustrations to Field Service Regulations, Operations, 1929
by Major Eady Lectures on Land Warfare by ‘A Field Officer” Military History for the Staff College Exam by Capt. E.W. Sheppard

14. If Germany Attacks by Capt. G.C. Wynne. This book is now rare but a
good summary of it is contained in The Dynamics of Doctrine by
T.T. Lupfer, Leavenworth Paper No 4

15. The Apostles of Mobility by Field Marshal Lord Carver is the best short
summary of the inter-war tank controversy. See also Liddel-Hart by B. Bond

16. We Planned the Second Front by Maj, J. Dalgleish


Major M. Green and John Plant

Adapted from Loopholes Journal No 13