The Signal Service in the European War of 1914 to 1918 – Chapter 7

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Chapter VII
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Chapter VII.


The Passing of the Shallow Bury. — Armoured Cable. — Ypres and Kemmel Deep Buries of Spring of 1916. — Preparations for the Somme Offensive. — Airline. — Construction in the Back Areas. — The 5.9 Proof (6 ft.) Bury. — The Grid System. — Protection of Signal Offices and Manned Dug-outs. — Army and Corps Control. — Methods of Burying Cable. — Mechanical Excavators. — Summary of the Situation at Close of 1916. — German Evidence on Buried Cables.

Apart from the question of enemy overhearing which occupied a considerable portion of the attention of the Signal Service in 1916, as in 1915, the principal feature of signal evolution in the later year was certainly the building up of the deep buried cable system.

The earlier shallow buries were intended to be splinter-, shrapnel- and traffic-proof only. It was recognized that a direct hit from a high explosive shell of any but the smallest calibre would in nine cases out of ten sever the cables or damage them sufficiently to cause faults and necessitate repair. In 1915, and even in the early spring of 1916, the percentage of direct hits had been so small that breaks in the 3 ft. trenches, which were then the rule, were few and could easily be repaired by the linemen available for the maintenance of the routes.[1] In January, 1916, a Divisional Signal Officer inspecting his lines after a minor attack, reports: —

"Every surface cable and airline was cut. An 'S' substitute line in a trench not filled in was cut by the direct hit of a small shell. A brass-sheathed quad[2] cable line four feet down in an open ditch was cut in four places. All lines buried 3ft. 6ins. held with the exception of one which was cut by a direct hit from a big shell. An armoured G.P.[3] twin line was hit by a 150-mm. shell, which lifted the cable so that you could get a hand underneath it. This cable ran to the most advanced trench and remained through."

This description of the investigation of the behaviour of cable in a small action is interesting in several ways.

To begin with, it gives some idea of the small percentage of direct hits received by a complete Divisional system at this date. This is exceptionally interesting in view of the marked change in this respect which was to come about within two or three months and which was indeed already setting in along the northern portion of the British line. Another respect in which the report has particular interest is the reference to various types of armoured cable which were now being issued in fair quantities for the first time.

Although it was intended for burying, it was natural that the new issue should be taken largely into use as trench and ground cable. The authorities who issued were, however, wiser than the officers who diverted the armoured and brass- and lead-sheathed cable from its original function. It soon became evident that the new cables, though more resistant to traffic, were not immune from the effects of splinters and shrapnel. They were also difficult to repair, needing the attention of specially-trained men. Their use as ground cable soon became quite obsolete, except in emergency at cross roads, and other much-traversed points beyond the limit of enemy shelling.

Even here, the steel-armoured cable alone was utilized, for both brass- and lead-sheathed cable were very easily bruised.

In the trenches, these cables could be used only in places where they could be partially protected, as for instance in the angle at the bottom of a trench nearest the enemy — or beneath the duckboard. Their use on a large scale as trench cable was restricted by considerations of bulk, and weight, and by the fact that far more than was at any one time available was always required for the buried cable routes.

The rival merits of the different types of armoured cable were amply tested in the months which followed. Each had its own good points, each its own disadvantages. Steel-armoured cable was liable to kink and was resilient and therefore somewhat difficult to handle. Brass-sheathed cable was rather more easily damaged, but handled with care was quite suitable for burying both by day and by night. Lead-sheathed cable was easily distorted, even by its own weight if carelessly laid, and required particularly careful handling, and level laying. Any inequalities in the trench in which it was laid would sooner or later cause faults and the trench bottom had, therefore, to be levelled off more carefully than could well be done at night. The lead cable had also to be handled very gingerly for fear of straining the sheathing and so weakening the insulation and the resisting power of the cable. It was, if carefully handled and laid, perhaps the best of all the cables, while it was issued in lengths containing many more pairs than the other two types. Some of the best buries of the early 1916 period were undoubtedly those in which the large twenty pair, lead-sheathed, paper-core, multi-cable had been used. However, owing to the drawbacks already enumerated, its use was confined to trenches which could be dug at leisure and in daylight. It could, therefore, be employed in the forward buries to a comparatively small extent only.

Armoured and brass-sheathed cables, on the other hand, were much more suitable for burying than "D5" cable, which was not originally intended for the purpose. The earlier issues were often faulty, but as time went on the quality of the cable improved, until a very good working standard was obtained. At first, only "twin" and "quad" cables were issued, but soon "seven-pair" cable was also standardized, and proved to be the most useful of all. From that time "D5" was practically restricted to the one or two pairs which, in almost every trench, were reserved for Signal Service purposes. Difficulty of identification of pairs was overcome by the adoption of a standard system of colouring of individual pairs or lines, and by careful labelling. The other great problem — that of repair — was solved by the training of large numbers of linemen as "jointers," and, perhaps even more, by the universal use of the cables, which forced all linemen engaged in the maintenance of "buries" to become familiar with armoured cable and able to mend breaks in it.

It was in the Ypres sector — always, since the early days of 1915, a favourite target of the German guns — that it first became apparent, in the spring and early summer of 1916, that deeper buries were required. Hitherto, direct hits on cable routes had been the exception rather than the rule, but, as the number of enemy shells poured on to the forward area increased, breaks in the buried cable became alarmingly frequent.

The 5.9 howitzer was already commencing to play a predominant part in the enemy's artillery preparation and retaliatory fire. Even a 77 mm. shell could be relied on to break the present buried cables if a direct hit was scored. Something more was required, if line communication forward of Divisional headquarters was to be reliable even in normally quiet times.

From the first, scarcity of labour had been the main obstacle in the way of the adoption of buried cable on a large scale. It had already been accepted as an axiom by signal officers that the deeper the cable was buried, the safer the route would be. Commencing with the traffic-proof buries of a few inches to a foot in depth, the tendency had ever been to go deeper and deeper, until the shallow splinter-proof buries had been standardized at a depth of 3 ft. From time to time, particularly energetic officers would achieve buries of greater depth than this, some being dug even to 4-1/2 ft. It was found, however, that this small measure of extra depth was of very little use. The routes were still not safe from a direct hit by a shell of average size. The only effect of the greater depth was to make the repair of breaks more difficult.

Shortage of labour was already restricting the number of routes which could be dug. Induction troubles prevented the concentration of all circuits in one or two deep buried routes, although such a policy was already visualized by many signal officers as the ideal. It was in early 1916 that the latter difficulty was first overcome by the manufacture and employment of twisted cable. As supplies of the latter and of armoured twin and quad cable increased, so the concentration of all routes into one, or, at most, two buries in each Divisional sector became a realizable ambition. The labour that had formerly been dissipated on comparatively numerous shallow buried routes was now concentrated on "a few deeper buries, and it was found by experiment that 6 ft. was the ideal depth. At that depth in normal soil the cables were safe from a direct hit from a 5.9-inch shell, and the 8-inch shell was not yet sufficiently common to be a dangerous menace to continuity of line communications.

Of these first, somewhat haphazard, deep buried systems, by far the most interesting historically are the pioneer examples laid down in the Second Army area at Ypres and Kemmel. In both cases, special factors led to the early adoption of deeper buries than were in use on the rest of the front. One factor common to both places was the intensity of the fighting which took place during the spring and early summer of 1916 along this portion of the British front. Shelling in the Ypres area reached an intensity far surpassing that of 1915 or on any other portion of the front at the same time. Shallow buries were broken right and left, in front and in rear. Circumstances thus forced the possibility of deep burying on the attention of the officers concerned, while other special features local to this particular theatre of war — the sewers of Ypres and the exceptional observation facilities afforded by Mount Kemmel — contributed largely to the comprehensiveness of the schemes adopted and the thorougliness of their execution.

At Ypres, signal communications had always been a problem of the greatest intricacy. The adoption of the shallow bury eased matters for a time, but this proved to be a very temporary respite. Deep buries through the town seemed to be the only alternative to a complete abandonment of line communication. Many lives had been lost, more linemen had been wounded or gassed, in endeavouring to maintain the system already in existence. The strain on the personnel of the Signal Companies of the Divisions manning the salient was too great to be borne, and by far the greatest number of breaks, and therefore of casualties, occurred in or about Ypres itself which acted as a concentration point for the enemy's fire. The problem of intercommunication through the town itself seemed insoluble until attention was drawn to the system of underground sewers which underlay the streets.[4] It was soon discovered that these would give good protection to the lines — for they were covered by no less than 6 ft. of road metalling. Once it was laid there was little fear of the cable being broken except by direct hit from shells of large size. A careful investigation of the whole sewer system soon showed that the laying of the lines was quite practicable, while only 300 yards of normal bury trench would need to be dug. In this way, the problem of communication through Ypres was solved. Labour was obtained and the execution of the system was put in hand at once. Signal personnel ran the cables through the sewers, and infantry working parties were employed in excavation of that portion of the route where a trench was necessary. The cable was here laid to a depth of four feet, the lines being protected above and below by sandbags. Road metalling was then piled back on top and the result was a route only slightly less safe than that in the sewers themselves.[5]

A similar sewer system on a much larger scale was also laid down in Arras, where, however, conditions of working were much easier than in Ypres. The sewers here were easy of access, large enough for several men to pass each other, and as much as 40 to 60 ft. underground. The cable used was twisted "D5" supported on insulators above the water level and the route was practically invulnerable. It was fortunate that it proved possible to substitute this system for the earlier buries. Many of the old pairs, particularly many circuits of "pernax" twin, were becoming very faulty and the old routes were rapidly becoming unworkable. On digging them up and examining the cable, it was found that the insulation of the "pernax" cable had completely rotted away, its unsuitability for burying work being thus conclusively proved.

The second of the pioneer deep buried cable schemes which is of particular interest was that laid down, mainly for artillery observation purposes, in and about Mount Kemmel. It was here that the first 6 ft. bury was laid down by the Canadian Corps. At the end of March, 1916, deep buried cables were accepted as a standard solution for the intercommunication problem on the Corps front in which this valuable observation post was situated. Work was at once commenced on a uniform system of deep buries on the whole Corps front and particular attention was given to the routes leading back from the hill itself. Into these were collected the telephone circuits from the observation posts which were scattered on and in the hill and the neighbouring spurs. Work was continued steadily from April 1st to June 30th, and during this time 420 miles of metallic circuit was laid six feet deep within this single Corps area.[6]

The systems above described, and others like them, were the forerunners of the more uniform buried cable schemes which were planned on the southern portion of the British front later in the year. It was in the north that the uses and the limitations of the deep bury were first systematically studied. The Ypres system was naturally anything but ideal for tactical purposes. The position of its exchanges, the route of its cables, were entirely decided by the network of sewers. These in their turn followed the plan of the town and were based on purely architectural and sanitary considerations.

At Mount Kemmel, again, the needs which the system served were very special. Everything was subordinated to the requirements of the artillery. Kemmel was an observation station par excellence. No general tactical considerations could be allowed to interfere with communications designed primarily with this in view. Indeed, all the northern buries of this period were improvised in a somewhat haphazard fashion as the exigencies of the moment dictated.

The shortcomings of such systems were not allowed to pass unnoticed. If an illustration is permissible, the growth of the buried system here and that which occurred later further south, may be likened in their broad outlines to the growth of two towns at different periods in the life of a nation. A good example is afforded by Sydney and Melbourne. The capital of New South Wales was founded when the colony was in its extreme youth and grew up bit by bit, street by street, like the cities of the Old World. It is a picturesque town, but by no means ideal as regards convenience and accessibility. In contrast, we have the newer and more business-like town of Melbourne, founded at a later stage in the history of Australia, and built on an ordered plan with streets running north and south and east and west. A further illustration of the same contrast can be seen by a comparison of the town plan of any ancient English town which has not been rebuilt on a large scale, with that of any of the newer towns in the west of Canada or the United States. In the same way, exactly, from a study of the failings of the earlier uncoordinated and unsystematic buries, the ideal buried system — the grid system — which came generally into use in the winter of 1916-1917 was evolved. The germ from which it sprang originated in the minds of officers who watched over and studied the earlier northern buries. It was developed on theoretical grounds by others, and finally appeared in the form which is shown in Plate XIII., which was accepted as the standard system of line communications in the forward area during stationary warfare. Much was to happen before the evolution and adoption of this standard system. As early as May, 1916, the centre of interest on the British front gravitated to the Somme area where the preparations for a great battle had already commenced. The first systematic offensive by the British Army on a grand scale was planned to begin on July 1st, 1916. Preparations for the battle started early in the spring and activity increased as the time for the casting of the die approached. The Signal Service, in common with the rest of the administrative services, rose to heights of feverish activity. In the preparations for the battle two things in particular needed great care and the exercise of careful forethought and creative imagination. The first was the preparation of an adequate and safe system of intercommunication within our own lines in the sector from which the assault was to be launched; the second was the successful bridging of "No Man's Land" during the assault and the carrying forward of the main line system as soon as the situation had settled down. The solution of the first problem in itself required months of unremitting work.

Our own guns had increased in number tremendously, and at last the supply of shells was in some measure commensurate with the needs of the Army. It was known that the enemy, too, was straining every nerve to increase his output both of guns and ammunition. That he was succeeding was only too evident from the tornado of fire under which our French Allies at Verdun had suffered a veritable martyrdom during the long months from February onwards.

It was hardly likely, in view of the magnitude of preparations involved, the increase in numbers and efficiency of the air services on both sides, and the length and intensity of our preliminary bombardments, that the British attack would come as a great surprise. If it did, the enemy artillery fire was likely to be comparatively feeble for some days, but as time went on and one of the main objects of the attack — the relief of the pressure on Verdun — was achieved, the weight of the fire directed on our own lines might be expected to increase from day to day. The French Signal Service authorities assured their British colleagues that nothing but 6 ft. buries could be expected to survive within the zone of heavy shelling. This, in its turn, now reached almost to Divisional headquarters. A colossal amount of labour was thus involved in the building up of a safe line system.

The quantity of work involved is not easily realized from the mere recital of totals compiled from statistics sent in by the units engaged. No figures of the preparatory construction by itself are available, but, during the preparation and the battles themselves, the amount of wire erected on overhead construction was no less than 43,000 miles. Over 7,000 wire miles of cable were also buried to provide the forward line system, and large quantities of cable were laid overground. The figures in themselves are stupendous when the size of the units upon whom the technical work fell is considered, but the difficulty of the task was increased tenfold by the circumstances under which the greater portion of the forward work had to be carried out.

It was no question of steady work carried out under genial conditions and Trade Union rules, in the comfort and safety of home surroundings. On the rear lines, airline sections and construction detachments were at work night and day in all weathers, harassed occasionally by long range fire, and spurred on to labour to the limit of their strength by a realization of the extreme importance and urgency of the work they carried out. No time could be allowed for rest, no leisure even for the grumbling so dear to the soldier's heart. Every man was worked to the full limit of his capacity all the time. The only reward of self-sacrificing work was the contemplation of a growing and efficient system. It was sufficient. As the last touches were put to the routes towards the end of June, all concerned might well be proud of the work they had done.

As the parties departed to their maintenance stations, to tasks elsewhere along the front, or to await orders for the work which might fall to their lot in pushing forward the routes in the wake of a victorious army, they left behind them a line system which was unique of its kind. It was soon to be surpassed by their own efforts and the efforts of their comrades in the battles of the later stages of the war, but none the less it was a triumph of skill, organization, and well-directed energy.

Forward of Divisional headquarters, the work was carried on under the circumstances always closely associated with trench warfare. Three months of preparation was only just sufficient to permit of a good system of buried cables being laid down. In April, 1916, orders were issued that future buries must not be less than 6 ft. deep. This decision was based on evidence provided by our French Allies and on our own experience. It had been abundantly proved that it was the last few inches that counted. 5 ft. was not much more secure than three, and it certainly took far longer to repair cable buried at that depth when it was once broken.

Buries at a depth of 6 ft. were immune from the direct hit of the dreaded 5.9 shell. In the Ypres operations in June a bury of this depth had been hit several times without being broken. The same day, the one weak spot in a Divisional route several miles long was neatly severed, although the area of insufficient protection only extended for a length of 10 ft. Again and again such experiences showed the danger of leaving any weak places at all.

The deep bury was thus accepted as the standard method of line communication, and during May and June every effort was made to complete such a system on the front of as many Divisions as possible. Once again, the question of the supply of cable was a serious obstacle to reform. Divisions possessing a good system of shallow trenches were unable in every case to obtain either cable or labour sufficient to replace this system with deep buries. The result was soon seen on July 1st. When the enemy's barrage fell on the area behind our front lines, communication remained through automatically, where buries were 6 ft. deep. Where they were less, line communication forward of Brigade headquarters, and often also between Brigade and Division, was intermittent. Such measure of continuity as was achieved was only secured with the greatest difficulty and at the expense of many casualties.

The striking superiority of the 6 ft. bury had already been demonstrated in individual cases in the desultory lighting of the earlier summer. It had been proved beyond doubt to our French Allies at Verdun. The lesson was now once and for all driven home to the whole of the Staff and Signal Service of the British Army. Given the necessary labour — and the demonstrations of early July were sufficient to secure this — and enough twisted cable — and the supply of cable was improving every month — and there need be little trouble with communications behind battalion headquarters either in stationary warfare or in the preliminary stages of an attack with limited objectives. The problem of forward communication during an attack and in semi-mobile warfare was a different matter, though much light was also to be thrown on these two questions during the Battle of the Somme.

As the offensive continued, the value of buried cable was indicated with even greater emphasis. Cases were recorded again and again of routes sustaining 30, 40 or 50 direct hits by shells from guns less than 8-inch calibre without interruption of signal communication. As the months passed and the battle continued, the area between battalion and Divisional headquarters was kept bridged with deep buried routes whenever the situation was sufficiently stationary.

As the use of deep buries became more universal, other modifications in Signal Service practice and even in Staff methods necessarily followed.

One feature of the 6 ft. buried system was the immense expenditure of time and labour involved in its construction. It was, therefore, comparatively rigid. The less time and labour required to build up a signal system, the more adaptable will it be. A deadlock at once arose with the general use of the deep bury. It was no longer possible for formation headquarters to move about at will. Already the shallow bury had tied down all but the most exigeant Staffs to permanent headquarters. With the installation of the deep bury, it became a physical impossibility for the signal office to follow its Staff about. Spurs could not be built off deep buries; if labour was available it was more urgently required on the main routes. Headquarters Staffs must settle down close alongside the main signal routes or they must risk overground lines which were almost certain to be destroyed in the first intense bombardment. Experience brought wisdom in its train. The deep bury persisted and the headquarters of formations and the major units conformed closely to the broad outlines of the signal system.

This system in the meantime was also modified by similar considerations and this modification was expressed in two main ways. One was in the evolution of the "grid" already referred to earlier in this chapter. So far as possible the new line system must permit of constant movements of formations, including that pernicious manoeuvre from the signal point of view — the "side-slip." The movements of formations sideways, crabwise, along the length of the front had always been a fruitful source of trouble to signal officers and of disorganization to their intercommunication system. The only method of ensuring that change of formation and change of front should take place with the least measure of interference with "Signals" was by means of the adoption of a skeleton network of front-to-rear and lateral main routes. At the junctions of these main routes would be commodious test or signal offices with comfortable living quarters for the personnel detailed to maintain the routes and to oversee the continual alteration of cross-connections.

At frequent intervals, along both front to rear and lateral routes, would be situated smaller unmanned test-boxes from which spare lines could be led up along protected ways on to terminals. By means of these off-shoots of the main system, connections could be made by the signallers and linemen of the units to whom the lines had been allotted either for the period of their stay in the area, or until the circuits were more urgently required for some more important purpose.

An important point was the relative frequency of the front-to-rear routes, and the selection of the best position for the lateral routes of the grid-iron trace. The former varied, of course, according to whether the system was serving a defensive or offensive front. Also, through-out the war, it was of course modified by conditions of supply of cable and of labour. The form generally adopted was that of one route per Divisional front. If an offensive was imminent and other Divisions likely to invade a particular front, extra labour was provided, and a sufficient number of extra routes were built. The position of the lateral routes was never in doubt once the principle of an ordered system was resolved upon. The main purposes served by the complicated trench warfare intercommunication system were those of "Command" and "Artillery observation and liaison." The obvious zones that required good service were those of formation and unit headquarters both of infantry and artillery. The exact position of these zones varied to some extent with the range of the chief types of artillery, both of our own and the enemy.

As can be seen from the illustration of the ideal grid system, four main routes were run in the depth of a Divisional sector. Nearest the front line were the forward centres serving the battalion headquarters and the forward observation officer; next came the observation centres at the forward edge of the battery zone serving battery headquarters and sometimes Advanced Brigade headquarters. The third route at the rear edge of our own battery zone served the artillery group headquarters and the greater number of Brigade headquarters, while finally the Divisional centres, just beyond the extreme limit of enemy shelling, served Divisional headquarters. This fourth lateral route usually coincided with the forward limit of the airline in the maintenance of the Corps. It was well into 1917 before this system had been fully developed. Later in that year, the same orderly system was continued further back with excellent results, and this policy, with slight modifications which will be referred to later, continued in practice until the end of the stationary period of warfare.

In the meantime, the same consideration which led to the crystallisation of a fairly rigid system of line communication along definitely- planned lines, caused attention to be turned also to the fortification of the manned dug-outs which formed the nodal points of the "grid," and also of the signal offices of formation and units.

Telephone exchange operating, the manipulation of delicate telegraph instruments, the docketing and recording of messages, even the constant adjustments in the cross-connecting field of a big test- point, are all delicate operations which call for the undivided attention of the personnel concerned. In the same way that the members of a Staff could not be expected to produce their best thinking combinations under the constant menace of extermination, so telephone and telegraph operators and linemen, if they were to do good work, required adequate protection.

In the constant bombardments which were the marked feature of the Somme battle, and also of the great position battles of 1917, it was essential that all vital points of the intercommunication system should be protected against the direct hit of everything but the very heaviest shells. The bury itself required protection against the heaviest shell normally used in large quantities in a barrage or in an area bombardment. This was done by making all buries 5.9 proof. Much more was required at ah nodal points in the signal system, as these, however well concealed, were liable to attract the deliberate concentration of long-range heavy artillery fire. Before the end of 1916 it was laid down as a principle that all signal offices should be sufficiently protected to be unaffected by the direct hit of an 11-inch shell. This was the ideal. Very often it was not nearly approached, but in all cases great efforts were made to afford security to the men who carried out vital roles in spots which were exposed to great danger of bombardment by the very nature of the system of which they formed an essential part.

During this year and the next, heavily concreted emplacements for test-boxes and for signal offices became a definite part of the signal communication system. As in 1915, these "nerve-centres" of the line system were made as inconspicuous as possible, but it had become recognized that in the face of aeroplane activity, and particularly of aeroplane photography, it was impossible to attain complete invisibility. Camouflage improved and was used to the greatest possible extent; strict orders were issued and enforced to prevent unnecessary traffic in the neighbourhood of signal offices and test offices. Everything possible was done to avoid attention. In spite of all precautions, both our own and captured enemy photographs showed up almost all main structures in the system of intercommunication as in that of fortification. This was still further shown by the accuracy of the enemy's long-range fire, particularly in 1917. It became gradually recognized that immunity could only be purchased by greater expenditure of labour, material and thought, in improvement of protection even at the expense of concealment.

All this extra protection both of cables and of offices could only be achieved by the exploitation of the labour of thousands upon, thousands of men. From the commencement of the era even of shallow buries, it had become clear that the Signal Service, kept down as it was to the smallest limit compatible with efficiency, could not provide the necessary labour. Infantry, Artillery and Pioneers, all were called upon in their thousands to help, and with the employment of vast bodies of non-signal labour the task became one which was beyond the power of the Divisional Signal Officer. Nothing in the history of Signals was destined to shift the balance of power to the rear more than the labour problems presented by the adoption of a universal deep buried system.

Already the resources of the Brigades were severely taxed to carry out the complicated series of trenches and works required in the forward area under stationary warfare conditions. R.E. working parties were busy day after day and night after night. Men, nominally in rest, were employed for a great part of their time either marching to, carrying out, or returning from, tasks. It is not surprising that an outcry arose when the Signal Service was obliged to put in a claim for a considerable quantity of Infantry labour.

The tasks in contemplation were so great that they could not possibly be dealt with by individual Divisions. Such a policy would also lead inevitably to that lack of continuity of policy which had already caused endless trouble. The necessary machinery for Corps and Army control already existed. In February, 1916, the senior signal officer at the Army had been created Deputy Director of Signals to the G.O.C. with the status of an Assistant Adjutant General and the rank of Colonel. About the same time, the senior signal officer of a Corps was appointed Assistant Director of Signals to the Corps Commander with the rank of Major (afterwards raised to Lieutenant-Colonel). Both officers had been relieved of their executive duties by the posting of other officers as Officers Commanding Army and Corps Signal Company respectively. The avowed intention of the reform was to "facilitate the supervision of signal communication both of the Signal Service and units of their formation and to secure efficiency and economy in the expenditure of material."

In both respects, no better subject for the exercise of these supervisory duties could have been found than the "buries" which grew and prospered under their hands in 1916 and 1917. Schemes were prepared and revised at Corps and Army headquarters. Labour was arranged for by Corps or Division according to the size and urgency of the scheme. Cable for burying was provided by the Army and distributed as required by the Corps. Records were insisted upon and kept up-to-date. Area personnel was supplied and kept up to its work by a system of the closest inspection. New methods of working were experimented with and particulars freely circulated. In every way, the work was co-ordinated and improved, and the value of a central authority and a central system of control was perhaps more thoroughly demonstrated here than in any other branch of signal work.

Finally, before passing to the lessons of the Somme battles in the forward areas and in the swifter-moving scenes of the more successful attacks, some consideration should be given to the evolution of methods of burying cable. From the first, thought and energy had been directed towards the diminution of the wholesale labour difficulties involved, but for a long time without more than local effect. Pipe-pushers were used with good results for passing underneath roads, railways, and other obstacles. Various ingenious devices were utilized for crossing streams and protecting stream crossings. Considerable use was made of iron water-piping and rails for strengthening weak places in the bury. An endless succession of water-tight and more or less shell-proof and easily accessible test- and joint-boxes were devised and patented by different signal units. The latter ranged from the simple joint-box, filled with paraffin wax or pitch, of the earlier shallow buries, to the elaborate test-boards and cross-connecting fields of the 1917 systems. In fact, as time went by, ingenuity constantly improved the technique of buried cable until the final standardized system was evolved which formed the basis of the recommendations embodied first in Technical Instruction, No. 11, of 1918, and later in Signal Training, 1919, Part IV.

The attempts to save labour by the use of mechanical means of trenching were not so successful. Comparatively early in 1915, a horse-drawn plough was used in some Corps with good results, but with the passing of the shallow bury, the usefulness of the plough also departed, if we except the special use which was made later of cable-burying tanks.

What was required for the deep buried cable system was the mechanical excavator capable of digging a trench 6 feet deep in reasonably quick time and with sufficient reliability to enable the time element in the scheme to be calculated with fair accuracy. In August 1916, the French Army was using with success two such excavators capable of digging a trench 6 ft. deep by 2 ft. wide at a rate of 20 yds. an hour. These machines were used in chalk country and their success seemed sufficient to warrant the adoption of similar machines in those Corps of the British Army which were also operating in chalk districts. They had their limitations, however. It was found that the type of wheel rendered them quite unsuitable for use in muddy ground such as was prevalent in the northern portion of the British front. The machines sank in the mud and — far from saving labour — they required the help of large labour parties to extricate them from the difficulties into which they often fell themselves. Their size and the noise they made also unsuited them for work in forward areas. Many buries were perforce carried out under conditions where night work and comparative silence were essential. In such cases mechanical excavators were quite useless and they were at once ruled out as regards forward work.

There remained then the possibility of making use of them out of sight and hearing of the enemy. There seemed little doubt that they would be of great use in the rear portion of Divisional areas and in that portion of Corps areas where, for particular reasons, burying was considered advisable. Six such tractors were, therefore, ordered from America in December, 1916. The first of these arrived in France in February of the following year and extensive trials were at once carried out, with varying results. Finally, in February, 1918, the Director of Signals reported that the excavators in their present form were not worth their keep. Owing to constant breakdowns and to the difficulty of obtaining spare parts, it was estimated that the personnel employed with them would have performed more work with pick and shovel in the same time.

Further trials were ordered but were never satisfactory, and with the passing of the summer of 1918 the occasion for the employment of the mechanical excavator ceased. If suitable machines and a supply of spare parts had been available in 1916, a considerable saving of labour could have been made in 1917, particularly since the Buried System was then extended far to the rear in the endeavour to counteract the increased activity of the enemy's long range guns and bombing aeroplanes. As it was, however, mechanical trench excavating was, throughout the war, always just a little behind what was required of it and was never of great importance.[7]

The foregoing discussion of the technique of buried cable has strayed far in advance of the general narrative. The end of 1916 and the conclusion of the Somme offensive saw the Signal Service definitely committed to a deep buried system lying in the main between battalion and Divisional headquarters. To the various junctions of a grid composed of the intersections of lateral and front- to-rear routes, all formation and unit signal offices within these limits were connected as desired. The original system, starting with 10 or 20 pairs, had increased to 50 or 70 pairs, according to the details of the situation which had to be met. A certain number of spare pairs had always to be provided to meet emergency concentrations, often of guns, more seldom of formations. The increase of the artillery with the Force had already permitted of the formation of the mobile Heavy and Field Artillery Groups which appeared, sometimes here, sometimes there, as harbingers of an approaching offensive. This accession to the number of guns engaged was accompanied by a greater precision in artillery methods which involved special lines for wire-cutting and many more observation posts than had formerly been considered necessary. When the situation was favourable, as at Mount Kemmel, special systems were built up which varied from the normal grid in proportion as the command system of lines was more or less subordinated to artillery requirements. In other places, where observation was from isolated posts or from the fire trenches themselves, lines from observation posts were concentrated through the forward test-boxes, and sometimes through battalion headquarters, to the Observation Centres of the battery zone.[8] Thus the ever-increasing demands of the artillery were accommodated more and more by the main command system and this was an additional argument for more complete control of artillery signals by the Signal Service authorities. The extension of the buried cable system beyond battalion headquarters was limited as a rule to the preparation for an approaching offensive. One fact which much reduced its usefulness near the front line in normal quiescent times was that buried cables, however deep, could not withstand shells from heavy trench mortars. Trench cable was therefore used to connect up important forward posts and company headquarters to the battalion, and also for lateral communication forward of the latter headquarters. Before an offensive of any magnitude, however, the deep buried system was continued by night work right up to a cable head in the front line. Often, indeed, it was taken right out by means of saps and mines across "No Man's Land" and even in some cases beneath the enemy trenches, the work being left to be completed after the assault had been launched.

Such cable-heads were usually the limit of reliable line signalling. Attempts were not made in this year to follow up the troops with deep buries, though when an attack had taken place and the situation had once more settled down to a modified form of siege warfare, the buried system was again advanced to the new battalion headquarters. In the preparation for the next attack it would again be carried forward to a cable-head in or near the new front line. This was, however, a normal procedure and was not marked by any features other than those already described. Labour was not available to permit of the buries being hurried forward in the interval immediately following an attack when the enemy shelling was comparatively weak. Many signal officers advocated the formation of a permanent labour party of 200 men per Corps during stationary warfare and 1,000 men per Corps during active operations. Some such system was already in being in the VI French Army and would have prevented the casualties inseparable from the pushing forward of the routes in the face of heavy fire from the German artillery, reinforced as it soon was by reserves rushed up as early as possible to the scene of a fresh offensive. The general tactical situation and the situation as regards man-power did not, however, permit of the adoption of the same policy in the British Army.

Within the limits already described the new system was a very safe one. It was, indeed, for the period which we are now considering, relatively safer than any system of signal communication had been since the war began. The anxieties of the Signal Service as regards line communication in the forward area during stationary warfare were almost removed. Occasionally a bury would be interrupted by the direct impact of an 8-inch shell; occasionally a signal office dug-out, or test-point, insufficiently protected, would be blown in by a projectile from a long range gun. In either case the interruption was a matter of a few hours or minutes only, and always alternative routes were possible in a well-devised and well-executed grid. So secure, indeed, was the system, that supplementary signal communication was seldom needed in this zone.

The Corps wireless station was able to confine its attention almost entirely to the control of the forward stations working under it, the Divisional central visual stations were able to be sited entirely with a view to picking up signals from forward stations during an offensive. In most Divisions, a supplementary visual communication scheme was formulated and stations were selected and heavily protected. In the most elaborate cases these took the form of a heavily-protected central receiving station with several periscopes and binoculars or telescopes aligned on to various forward transmitting stations sited near the positions of the Divisional and Brigade observation offices. These intermediate stations were themselves fitted with receiving, apparatus devised more with the idea of receiving from any position within their field of view than of communication with any particular fixed stations. The visual system was, however, seldom needed to reinforce or replace the line system further to the rear than Brigade or even (towards the end of the year, when the deep buried system had developed to its full extent) battalion headquarters.

Before leaving for a time the study of the evolution of the buried cable system, it will be interesting to compare the experience of the German higher command with that of the British and French armies. In a report on the Somme battles, the enemy attributes his failure to withstand our initial attacks mainly to the failure of his telephone system, and the comparative absence of alternative methods of communication such as visual and wireless. The latter aspect of the question is of interest in connection with the facts related in the following chapter, but as regards the line system, generally, his conclusions are also very applicable to the experiences of the British Signal Service. The German report on the Somme battle stated definitely that "telephone communication cannot be maintained unless routes are systematically buried not less than 10 ft. in the open and 6 ft. below the sole of a trench." This sweeping statement was a tribute, both to the power and thorougliness of the British artillery preparation, and to the enemy's confidence in a capacity for elaborate fortification which made it possible for him to contemplate such a scheme as a realisable conception.


  1. The only marked exception to this rule was the Ypres salient. Here the shelling was so intense that the shallow buries were often broken by direct hits. The nature of the country was, however, not suitable to the development of the deep bury, and for some time signal officers had to devise as safe a system as possible by alternative routes in shallow trenches.
  2. Armoured cable with four pairs.
  3. Gutta-percha insulation.
  4. A small Belgian boy was paid to go through the sewers with a line, since they were too small to admit of the passage of a full-grown man.
  5. The sewer system at Ypres was finally destroyed by the enemy's 17-in. howitzers. It was not a great success as the sewers were nothing like big enough.
  6. The work begun by the Canadian Corps was completed by the IX Corps.
  7. In justice to these machines it should be recorded that occasions did occur when they did good work. In V Corps area in 1918, for instance, several miles of first-class cable trench were dug in hard clay and chalk in the Toutencourt area. Buried communication was established for some 2-1/2 miles forward of and 2 miles behind Divisional headquarters. The impression created here was good and with proper spares for maintenance much better and more general results might have been obtained.
  8. The introduction of central observation exchanges in 1916 was undoubtedly the greatest reform in artillery practice so far as it affected signals. By means of the concentration of lines from individual O.P.'s to these central points, it was possible to make the most universal use of the limited number of observation posts available. For the successful carrying out of this plan, central control of artillery lines was essential; the policy could only be carried to its logical conclusion by close cooperation and by the full utilization of the facilities offered by the main command signal system.

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