The Signal Service in the European War of 1914 to 1918 – Chapter 16

«--	The Signal Service in the European War of 1914 to 1918 Chapter XVI	--»
Chapter XV

Chapter XVI.

SIGNALS IN THE AUTUMN ADVANCE.

SYNOPSIS.

British Signals in the Marne Advance. — Adaptations to Suit the French Signal System. — Two Distinct Phases of the Advance. — Mobility the Chief Essential. — Army Signals and Mobility. — Concentration on One Main Route. — Standard Forward Offices. — Construction across the Devastated Area. — Corps Signals in the Advance. — A.D. Signals' Three Responsibilities. — The Corps Signal System. — The Transition from Rigid to Mobile Warfare: A Dangerous Period for Signals. — Co-ordination between the General Staff and Signals Solves most Difficulties. — The Forward Communication Centre System.— Use of the Abandoned Divisional Cables. — Their Replacement by Air Line. — Reconnoitring of German Permanent Routes. — Corps Wireless. — Corps H.A. Signals. — Dominance of British Artillery. — The Last Buried Cable. — Divisional Signals in the Advance. — General Policy. — Divisional Artillery Signals. — Three Types of Country Traversed. — The Line System. — Trouble with Tanks, Kite Balloons, Traffic and Marauders. — Brigade Lines. — Supply of Cable. — Salving. — Lateral Lines. — Forward Wireless in the Advance. — Stepping-up. — Continuous Wave Wireless. — Special Uses of Wireless. — Difficulties Decreased and Opportunities Increased. — Pigeons, Messenger Dogs, etc., Unimportant. — Mounted Orderlies. — Aeroplane Signalling. — Visual. — Cavalry Signals. — Finale.

As the last great action in which a British Corps took part during the retreat was with the French Armies upon the Marne, so, in July, 1918, the XXII Corps was thrown in on the same front to add weight to the French offensive which rolled back the German armies from the countries they had overrun during the June battle. As before, the most interesting features of the signal practice arose from the isolation of a British Corps amongst French formations. The French intercommunication service worked on lines which differed fundamentally from British practice.

They relied almost entirely upon the telephone for line communication and the chief alternative method used in the French Army was continuous wave wireless. Line telegraph and spark wireless were both disliked and used as little as possible. The latter was confined entirely to the area forward of Divisional headquarters, the former was not used at all for lateral work.

A British formation set down in the midst of a French Army was therefore obliged to modify its normal system in several particulars. In the case of the XXII Corps, in the advance from the Marne in July, rear communication was b}' telephone only, except for one superimposed Morse circuit back to the headquarters of the 5th French Army. Lateral liaison with the French Corps and Divisions was either by telephone over lines specially laid by the British signal sections, or by C.W. wireless. For the latter purpose the French Radio Service placed a high-powered C.W. set at Corps headquarters, and this set was also used for alternative communication back to Army. Continuous wave sets were alone used for wireless communication up to Divisional headquarters and, forward of this, British spark wireless sets were kept silent until half an hour after zero hour of the first day of the attack.

The working of the line system itself was modified in two ways by the circumstances peculiar to the attack. The exchange operators with the British formation had been taught a certain amount of French, but in spite of this preparation they still experienced considerable difficulty in passing calls which had to go through several French exchanges. This trouble was due to quick talking and colloquial expressions used by the French operators. It was overcome at the Corps exchanges by the attachment of a few interpreter operators who were given a local telephone on the Corps switchboards and were put through to the French exchange from which they followed up the call until the attention of the required office had been secured. They then informed the British operators who put the Staff through. Unfortunately the number of these men who were available was very few. The only source from which they could be drawn was the very small establishment of listening posts which were thrown spare by the advance. There were sufficient to supply the Corps exchanges, but the Divisions were obliged to do without and much delay resulted.

The second modification of the line system was the use by the French of cables slung on pickets three or four feet high. Seven or eight cables were used on each of these routes and it was claimed for them that they were much more immune from bombing and shelling than either open wires, ground cable, or poled cable. Our allies strongly recommended the adoption of these routes by the British Corps, and eight miles of eight-pair route was built in seven days over rough country consisting of vineyards and woods. In this time the preparation of all materials is included. The routes gave good service and the contention that they were less liable to destruction by enemy action appeared to be correct.

The supply of cable also presented much greater difficulty than usual. The Corps had brought with it a small reserve supply when it came into the area by rail. No further supplies could, however, be obtained for four days from the date of requisition, and units were obliged to rely to a much greater extent than usual upon their establishment.

As far as the conditions of the battle were concerned, it proved to be easy to maintain line communication as far forward as battalion and battery headquarters. Owing to this shortage of cable, however, only a very slender system could be built. A Brigade system consisted normally of an omnibus line to which all three battalions connected themselves by short spurs whenever their headquarters settled down. Every effort was made to save cable, but the chief source of expenditure, which could not be reduced very much, was that on lines between batteries and O.P.'s.

In spite of the utmost economy the reserve rapidly approached vanishing point and it was only by borrowing some 50 miles of twisted cable from the French that the line system was kept intact until the arrival of the fresh stocks. It was by such occurrences that the necessity for organizing cable supply was driven home, and one of the chief lessons of this battle was the recommendation that in future cable should be supplied as regularly as ammunition. Indeed, it was suggested that a supply of cable in railway trucks should be attached to the ammunition train, issues being controlled by A.D. Signals, but the supply maintained by the O.C. train and replenished at each trip to the Base.

With the above exceptions the signal system in the Marne Battle was like those of the later battles of the main British offensive, and its features are best described in common with those of the latter. The success of the French offensive opened up vistas of possible victory which encouraged the Allied higher command in their determination to press the enemy both on the French and British front, and on August 8th the British armies joined battle with the German defenders of the line in front of Amiens. The general offensive which followed was sustained until the German nation acknowledged defeat by the signature of the Armistice on November 11th, 1918.

The struggle between these dates can be divided into two distinct portions, which presented rather different problems to the Signal Service for solution. Until the forcing of the Hindenburg Line and its reserve positions at the end of September, the enemy endeavoured to defend himself in a series of strongly-built defence zones from each of which he could only be dislodged after a position battle which rivalled those of 1917 in intensity. In between such battles the situation was semi-fluid, the German rearguards retiring slowly and methodically under the pressure of our advanced troops and mobile artillery. After the great battle of the Hindenburg Line the enemy's retreat was more hurried and the only pauses occurred at such natural lines as adapted themselves to defence without much preparation. The most serious of these obstacles were, of course, the canal and river lines. As the days wore on, the checks became less frequent and less sustained, the British advance accelerated, and the retreat of the enemy became more disorganised, approximating more to a rout than a calculated retirement. During this last stage of the war something approaching mobile warfare set in, and the main problem which confronted the Signal Service was the physical difficulty of keeping up with the advancing troops. Allied to this second phase, and even surpassing it in speed of action, were the voluntary withdrawals to the north of the decisive front when large tracts of country were ceded to our troops, often without the slightest semblance of resistance. Here, again, the chief difficulty encountered by the Signal Service was that of adapting an organization which had grown up under position warfare conditions to the needs of a mobile force.

The recognition of this problem as a most serious difficulty and a tribute to the way in which it was solved are contained in the following paragraph from the official despatches of January 7th, 1919:—

" The constant movement of the line and the shifting of headquarters has again imposed an enormous strain upon all ranks of the Signal Service. The depth of our advance, and the fact that during the latter part of it the whole of the British armies were simultaneously involved, made the maintenance of signal communications most difficult. The fact that in such circumstances the needs of the armies were met reflects, the highest credit upon the zeal and efficiency of all ranks."

In many respects the signal system of the advance much resembled that already described when discussing the less general advances which accompanied the battles of 1917, and particularly the battle of Cambrai. It differed in extent, however, and in the incorporation of the lessons already learnt during those actions. For the first time the area of movement affected the whole of the fighting forces as far back as G.H.Q., while — as stated in the despatches— problems were much intensified by the fact that at times the whole front was affected and it was, therefore, impossible to make up local deficiencies by reinforcements and stores from other portions of the line. The way the lessons of former offensives and of the spring retreats had been seized and turned to account was demonstrated by the success of the forward signal units in coping with the special problems due to the universality and the speed of action of a great offensive such as had never been matched in any previous battle. The principles followed were based upon the experience of 1914 and 1917 as summarised in S.S. 191, but to the concentrated wisdom of these pages had been added the lessons of the earlier battles of 1918. The result was a system of forward signals entirely adequate and at the same time speedy of construction, simple of maintenance, economical both of men and stores, and divested of all superfluities.

While the establishment of an advanced G.H.Q. from which operations were directed much increased the work of G.H.Q. Signal Company, it was within the armies again that the effects of the constant movement made itself felt with decisive effect. The comparative mobility of the operations of the spring and early summer had taught very useful lessons to Army headquarters as well as to the formations in front of it. In two respects especially had this been so. The Army advanced offices which, before the retreat, had been composed of large 60-line switchboards, had had the latter replaced by standard multiple boards, and the offices made portable in every possible way. The Army wireless station also had been taught to dismantle quickly, lose no time on the road, and re-erect as speedily on reaching the site of the new headquarters. Both these lessons added greatly to the chances of success of the Army signal units in the autumn battles.

Movements of Army headquarters commenced to take place soon after the beginning of the advance. In some cases headquarters were situated at awkward corners of the areas they controlled, in others, sideslips took place for other reasons. In all, two or three moves took place and were attended by the usual extra work. This was, however, reduced to a minimum, as experience improved the portability of the forward offices and permitted of the crystallization of the exact form of skeleton communication system which was best suited to deal with all urgent needs and yet contained nothing superfluous.

Army headquarters, like the headquarters of the Corps, Divisions and Brigades, learnt to manage with the essential minimum of liaison. A typical forward system which was very successful in operation consisted of one telephone circuit each to G.H.Q., Advanced G.H.Q. and flank Armies, two to each Corps in the Army and three to the rear Army office. On all of these circuits, except one to the rear office, Morse was superimposed. At the forward office three multiple boards were set up and a carefully-pruned system of Staff phones was installed. So carefully were these forward offices standardized and so exactly was the routine of installation insisted upon, that in the later moves 24 hours notice was quite sufficient to ensure that the Staff could rely on finding the above minimum of intercommunication ready for them in working order on their arrival at the new headquarters.

The circuits were carried forward on a main route which was the first care of the construction company and was built down the centre of the Army line of advance. In the earlier slower phase of the advance this route was of 24 wires, at a later stage the German permanent routes were utilized and reconstructed on a 16-wire basis. The speed of advance of the Army line system was limited by the speed of construction of these large overhead routes. When the advance was rapid it outran construction and the only way in which the situation could be met was by rigid adherence to instructions limiting construction work to main routes only. The commanders of subordinate units could no longer be given the telegraph and telephone facilities they had formerly enjoyed. The main routes were pushed on with all possible speed but all intercommunication forward was limited to these and to such spurs of the Corps and Divisional systems or of the German permanent line system as could be reconstructed without loss of time or the use of large quantities of labour.

It was recognized by the Signal Service, however, that as many intercommunication facilities as possible should be given to the units scattered through the Army areas, and their wants were catered for to some extent by means of "Public" telephones and a reinforced D.R.L.S. The former were installed at each signal office and were at the disposal of all officers wishing to transact legitimate and urgent army business. The latter was modified to meet the peculiar prevailing conditions. It was no longer possible to deliver to units here, there, and everywhere, but the offices of the various Area Commandants were utilized as the fixed centres to which letters could be delivered by motor cyclists. A General Routine Order was accordingly issued instructing all units not directly served by the main D.R.L.S post to send in to the office of the local Area Commandant with and for their mail. Urgent traffic was disposed of once or twice daily by circular runs to these offices and a fairly efficient liaison was thus maintained throughout the Army.

In such ways the Army system adapted itself to the new phase of warfare and proved far less rigid than might have been expected. The only innovation in signal practice besides the standard forward office and the adoption of the multiple boards, was the use of Wheatstone between forward and rear offices. It has been placed on record by the officers concerned that much delay might have been avoided if similar Wheatstone sets could have been issued to Corps headquarters also.

As the Armies moved forward across the broad devastated area, both signal construction companies and motor cyclist despatch riders suffered from the bad roads and the lack of bridges to span canals and rivers. Usually, only one or two possible routes were available from front to rear. Lateral roads were still less common, for Corps and Army Troops were far too busily engaged upon the routes leading forward to be able to give any attention to these side issues of traffic. The condition of the roads was very bad apart from recent deliberate destruction, while the work of the enemy engineers had been so consummately thorough that, at times, the construction companies were obliged to revert to horsed transport and cross-country detours in order to get ahead at all. At each pause in the operations, when the Army halted temporarily on a fortified or river line, signal traffic increased in volume until it even surpassed that of the more stationary signal system of the previous year. In the month of August as many as 20,000 telephone calls were recorded on the system of a single Army in a 24-hours period, while, in November, when the last advance ended with the Armistice, the same Army once more boasted 140 subscribers on its main telephone exchanges.

It was from Corps headquarters forward that the element of mobility in the new situation became absolutely predominant in its effects. It was the A.D. Signals, Corps who in reality controlled the forward signal policy of the Divisions during these last four crowded months. The Corps system itself was modified to a considerably greater extent than that of the Army. The frequency of the moves of Corps and Divisions was rivalled by the distances covered at each move. On one occasion a Corps moved 35 miles at 24 hours' notice. This was an extreme case, but moves of 20 miles or so were not uncommon, while divisions moved every few days in bounds of five to 10 miles.

Each A.D. Signals of a Corps was faced with three distinct responsibilities. He, or his O.C. company on his behalf, must ensure the essential minimum of intercommunication between his own headquarters and the headquarters of the Divisions in the Corps: he must ensure an efficient signal system for the heavy artillery serving with his Corps; finally, and this was perhaps the most important of all his functions, he must co-ordinate the systems of the Divisions in front of him and arrange matters so that his own line system could be carried forward in the future along one or other of the main Divisional lines of communication.

The first two problems were largely a matter of careful organization of the personnel at his disposal. All subsidiary offices were closed down and the attention of all his outdoor personnel was concentrated upon the main routes. Similarly, indoor personnel was organized to form two main offices, the more advanced of which could again be split up to enable a stepping-up process to take place.

The principle of the maintenance of a minimum of efficient intercommunication along a central route which finally overcame the new difficulties raised by mobile warfare was not achieved without some mistakes being made. Both in Corps and Divisions the less important members of the Staff were tardy in relinquishing the telephone rights which they had come to claim as their due during stationary warfare. In this respect, some formations were worse than others, and it is noteworthy that the worst offenders in the early stages of the advance were such Corps and Divisional Staffs as had not been involved in the recent semi-mobile engagements at Cambrai, the Somme, the Lys, or the Marne.

The initial tendency to treat the engagements by which the successive German defence zones were breached as being similar to the slowly-moving battles of the position warfare period added much to the perplexities of the senior signal officers. It was, however, gradually eradicated from the minds of the Staff as action accelerated and moves of headquarters became more frequent and far-reaching. It was obviously impossible to build many miles of heavy routes in two or three days: it was equally evident that transportation difficulties would not permit of the forward movement of cumbersome offices. Gradually, as the situation developed, these initial obstacles to free movement died away of themselves and everyone concerned became reconciled to the idea of the speedy establishment of a minimum of signal communication as the dominant characteristic of the mobile warfare signal system.

The lines on which the new problems were solved had already been indicated in S.S. 191. With some slight modifications, the principles of this book were carried out with a success which could not have been attained by any other method. The two factors of the problem were as usual the General Staff and the Signal Service policies. By this date it was generally recognized that these were essentially interdependent and with the admission of this fact by both sides the main difficulties of the situation as regards signal communications had disappeared. Co-operation was the order of the day: by means of co-operation and forethought the duplication or alteration of signal routes was practically done away with and the element of uncertainty of direction eliminated from the situation so far as was possible.

With the small proportion of signal personnel available to serve the needs of the army, it was essential that none of the work done by the construction detachments should be wasted. Airline and cable sections had been reduced to a minimum establishment, while the number of units was no more than equal to their responsibilities. To ensure the rapid and efficient following up of the Divisions with a safe line system, the two airline sections of the Corps were fully occupied in the carrying forward of one main route. Similarly, the cable sections of Corps and Divisions were worked to the limit of their endurance in order to maintain the necessary minimum network of lines. From the first, it was clear that Brigades, Divisions, and Corps must advance, each along one main preordained route, and that these routes must be fully advertised well in advance and changed as little as possible.

It was here that a well-considered and carefully thought-out policy on the part of the General Staff proved to be the saving of the Signal Service. It had been amply demonstrated in the March retreat that, where forethought was exercised and efficient control exerted by the higher formations, good intercommunication could invariably be assured. Conversely, it had been proved again and again, that where forethought was absent and control not exercised, there chaos prevailed. The lesson had been learnt and now each Corps advanced along a definite line laid down in advance by the General Staff and 'Changed as little as the situation would permit.

The names of the principal towns and villages near the centre line of the formation area were published in General Staff orders and, whenever possible, these actual positions were utilized by all formations as important nodal points on their intercommunication routes. The signal route of one Division almost invariably followed the line laid down, and it was along this route that the Corps advanced its own air line, reeling up the cable as it was replaced by this more stable conductor.

The chief difficulty in the way of economy was the fact that the higher formation needed one only out of two or three routes in front of it. The others were therefore thrown spare after very little use. This was overcome by the adoption of a system of forward offices or communication centres. The advanced signal office of the Corps was kept as far up along the Corps-Divisional line of communication as possible. When the Division along whose route it was following moved forward, a Corps advanced office was again established close behind the new Divisional headquarters and spurs to Divisions to left or right of the central line of advance were thus kept as short as possible. The same principle was adopted at Division and Brigade, arid the main feature of the line system of the advance was thus one main route per Corps which was made as heavy as time and personnel would permit and from which radiated smaller spurs to flank Divisions. From Divisional headquarters, again, longer lines ran to forward communication centres from which short spurs branched off ta Brigades, Similar forward centres in Brigades completed the system and kept down the expenditure of cable to a minimum.

Comparative skeleton line systems from Corps to Brigade with and without forward communication centres are shown in Plate XX. These are drawn to scale and give a very good idea of the saving of labour and cable effected by the adoption of the former method. Equally great advantages in the direction of ease of maintenance and greater safety are also self-evident from a comparison of the two methods.

The first problem with which A.D. Signals of a Corps was faced — the maintenance of the necessary minimum of communication between Corps and Division — was thus simplified to some extent by the presence of the main cable axis which had been laid by the Division that happened to be advancing along the Corps route. Attached to the headquarters of this Division, and following close behind it, would be a Corps cable section. It was the duty of this section to make the hastily laid Divisional lines more safe. Thus, as they passed behind Divisional headquarters, they were in a fit condition to act as the main Corps route until, in due course, they were replaced by the Corps airline. If the advance were unusually fast, it might well be that the Division might not be able to lay more than one "earthed" and one metallic circuit to serve its own needs. It was then the business of the Corps cable section to reinforce this too slender trunk line. This might be done either by laying another single cable or by adding an extra twisted pair. The minimum aimed at for the Divisional route in the slower intervals of the advance, and for Corps routes at all times, was three twisted pairs.

The route would also frequently require strengthening and (unless the lines were well slung on hedges) it was usually necessary to pole them before they could be considered safe. If the advance was slow, on the other hand, the Divisional cable detachments were themselves able to achieve a safe line. The Corps cable section could then often work in advance of Divisional headquarters, thus relieving the Divisional cable wagons of the rear portion of their work and enabling the latter to keep well ahead of Brigade headquarters. It was on these advanced Corps cable sections that the brunt of the more dangerous work in bombed and shelled areas fell, and several well-earned distinctions fell to the lot of the officers and men comprising them. Their presence forward of Divisional headquarters, also, was conducive in the highest degree to good feeling between the signal units of the Corps and its Divisions.

Where advances were speedy and movements of headquarters rapid and carried out over great distances, much trouble was experienced in speaking over the cables which usually formed a considerable proportion of the very lengthy lines between Corps and Divisional headquarters. It was not an uncommon thing to have a Corps working to its Divisions over distances of the order of lo to 20 miles of which two-thirds might be airline and the remaining third poled or hedge cable. In such circumstances speech was almost impossible, unless the lines were very carefully built or laid. It then became more than usually important for the airline construction to be hurried on. Just as, in the Army area, the advance of the signal line system was limited by the speed of construction of the permanent routes, so, in the Corps area, the speed of advance of the lines was not always commensurate with that of the more mobile headquarters in front. The general plan was to build forward a 12-wire route to take the nomial traffic of the Corps. If movement was comparatively slow, the whole 12 wires were taken forward at once; if rapid, four wires were pushed ahead with all possible speed by the best men of the construction detachments, while improvised parties, made up of all the odds and ends of signal personnel that could be collected, followed as quickly as possible with the remaining eight wires. Everything possible was done to speed up construction. In the chief battles permanent routes were dug well forward before zero hour, pot- holes being dug and carefully camouflaged and stores laid out.

A typical record that has survived, was the building of 53,000 yards of 12-wire hop-pole route by the airline sections of one Corps in 16 days This route was put up under difficulties, for, owing to the shortage of stores, it had to be taken straight forward across the devastated country. Roads were few and far between, and the country in between the roads was impassable for wheeled vehicles. In many cases, the "carries" were as much as 1,000 to 1,500 yards over torn and shell-pitted country and the work involved was twice as much as would have been expended in building the same length of route through ordinary terrain.

In some cases the roads were so congested that it was difficult even to get the poles and other stores out of the lorries and wagons. In others, floods interfered very much with the working parties. Stretches of the country had been inundated by the Germans before the retreat, and the essential lines had to be carried forward over the swamped areas by the help of pontoons.

As the advance passed out of the devastated areas into hitherto untouched country, German permanent routes in more or less disreputable state of repair passed into British hands and these were utilized by Divisions and Corps alike. Here, once again, the virtues of co-ordination were seen and, where organization was good, Corps and Division vied with each other in obtaining information about the German circuits in their area and in disseminating such information to anyone to whom it was likely to be of use. The enemy had sawn through most junction poles and much damage had been done to routes where railway trucks had been blown up, or mines had been exploded at cross roads and at the entrances to villages and towns. It was found that routes along main roads had been most destroyed, while time had apparently not permitted of such thorough damage being done to cross-country and railway routes. To a certain extent this played into the hands of the British Signal Service. German bombing planes were operating in swarms along the main roads in Corps and Divisional areas, and the enemy was now shooting almost entirely by the map. If roads and valleys were avoided, it was found that routes were usually safe except from stray haphazard shells.

The reconnoitring of the German routes presented a distinct problem and was dealt with in different ways by different Corps and Divisions. The most normal method was to detail one or two officers of the Corps to go forward on motor cycles and make as rapid a survey as possible of the routes which appeared to run in a suitable direction. A common method employed by Divisions was for a senior signal officer to reconnoitre forward in the O.C. Signal's car. Although the main roads were usually blown up at all road junctions, by-roads had been destroyed much less systematically and often gave access to the areas in the occupation of the most forward British troops. The weather, also, was uniformly good and it was often possible to use field tracks to debouch from one side road to another, while, if the car did by any chance become bogged, there was always a good prospect of help either from troops or from civilian inhabitants who were only too eager to help their deliverers in any way.

A yet more ingenious means used with success by one Corps in favourable weather was an aeroplane survey. Early one morning one of the pilots of the Corps R.A.F. Squadron flew a signal officer over the whole area over which the Corps was advancing. In less than two hours a fairly detailed reconnaissance had been made of the signal communications existing both in the zone occupied by our own forward troops and in that still held by the enemy rearguards. It was a bright sunny morning with an unusually clear atmosphere. The shadows caused by the poles and the light reflected from the wires enabled the whole system to be seen and sketched. It was even possible to distinguish the individual wires and their state of regulation. The sketch which was brought back by the observer was later proved to be correct in every detail and it was quite clear that, given favourable weather and a spare aeroplane, the ideal method of surveying forward routes had been discovered. The saving of time was all-important at this period of the year when the days were short and only a portion of the hours of daylight could be utilized for work owing to the congestion on the roads.

The Corps line system just described was reinforced by a wireless chain which consisted usually of a main directing station at Corps headquarters and an advanced station which was usually at Advanced Corps headquarters or at the headquarters of one of the Divisions in the line. In some Corps an extra station was obtained and manned and used as a Corps message station, thus permitting the directing stations to give their whole time to the control of the forward stations. Wireless was not, however, used to any great extent as an outlet for traffic between Corps and Division except at such times as the advance had outrun the line system. This was not likely to happen in a Corps which was advancing along a Divisional route. A marked exception was, however, provided by the Canadian Corps who relied upon wireless throughout as an auxiliary system to take surplus traffic that could not be accommodated on the Corps lines. An' interesting synopsis of the wireless traffic handled by the stations of this Corps is given in Table XII.

Table XII
Canadian Corps Wireless Traffic during the Advance.
Date.			Corps.	Divisions				Total.
				1st.	2nd.	3rd.	4th.
Aug.	26th	. .	85	—	26	2	—	113
Aug.	27th	. .	75	—	10	62	—	147
Aug.	28th	. .	82	9	14	105	—	310
Aug.	29th	. .	70	56	—	66	—	192
Aug.	30th	. .	52	43	—	—	—	95
Sept.	1st	. .	89	0	4	—	11	104
Sept.	2nd	. .	92	68	16	—	104	280
Sept.	3rd	. .	86	50	26	—	111	273
Sept.	4th	. .	80	50	32	—	115	277
Sept.	5th	. .	69	—	—	—	69	138
Sept.	6th	. .	—100	—	—	—	38	138
Sept.	7th	. .	76	—	—	—	—	76
Sept.	8th	. .	106	—	—	—	—	106
Sept.	9th	. .	—65	—	—	—	—	65
Sept.	10th	. .	—63	—	—	—	—	63
Grand Total (Canadian Corps, August 26th to Sept. 10th)								2523

Comparative Totals
Calculated average total per day if Corps and all four Divisions engaged	300
Calculated average total per day, Corps	81
Calculated average total per day, Division	45
Calculated average total telegraph traffic at Corps headquarters, same period	5000
Calculated similar total for Division	660
Calculated daily total D.R.L.S. at Corps	2200
Calculated daily total D.R.L.S. at Division	500

While mobile warfare exercised a consolidating effect on Divisional artillery and infantry signal relations, the reverse was seen to be the case with Corps heavy artillery and Corps headquarters signals. Two quite different artillery dispositions were made in different Corps. In the one case, the control of certain heavy brigades was decentralized to Divisions and the responsibility for the signals of such Brigades naturally fell upon the already overburdened Divisional signal officer. In the other case, Corps headquarters retained control of all the heavy guns. The tendency with heavy artillery was naturally for the heavier guns to lag behind the more mobile formations in a quick advance, but to collect again when the advance slowed down or stopped before any of the successive lines which the enemy endeavoured to hold. The result of such differential movement was the concentration of the attention of the H.A. signal personnel on the construction, manning and maintenance of a special system of their own. The forward exchange system was utilized in this case also and one main route of four pairs of poled cable or airline was built forward on either side of the Corps area. These were led into forward exchanges which served the various Brigades of the two groups. The inadequacy of the Corps H.A. signal establishment was soon seen and the situation was only saved by the attachment of a cable section from the Army or the Corps. The lines from the C.H.A. central exchange to the forward exchanges were very long and maintenance was very heavy, this being due more to traffic than to enemy shelling. It was only by the utmost exertions of the sections that the trunks between the exchanges could be built and kept through. It was usually necessary to call upon the R.G.A. Brigade signal subsections to lay and maintain the lines back from their headquarters to the forward exchanges, in addition to their normal work forward to the batteries. The inadequacy of the C.H.A. signal section was perhaps the chief lesson of the advance as it affected artillery signals.

The use of continuous wave wireless with heavy artillery was very marked during the advance, and might have been much more so, had the necessary number of stations been available. Where decentralization of Brigades had taken place, it proved impossible to lay lines between R.G.A. Brigade headquarters and C.H.A. headquarters in addition to the necessary command lines to the Divisions under which the Brigades were working. All line traffic had to pass via Division and Corps headquarters and was much delayed in consequence. Continuous wave wireless was utilized in such cases to supply the direct communication desired and as many as 30 to 40 messages were passed by this means every day.

While the responsibility for the two signal systems just referred to rested with the A.D. Signals of the Corps, he was fortunately able to delegate this work to two senior officers of his company. The O.C. Corps signal company was usually given charge of the Corps system and the administration of the company. The O.C. Corps H.A. section confined his attention altogether to the heavy artillery signal system. A.D. Signals himself was therefore able to devote a considerable portion of his time and energy to co-ordinating the Divisional communications and assisting the Divisional signal officers to anticipate the line of advance in good time and keep the Divisional route well ahead of the immediate requirements of his Staff.

The problems of forward signals are more susceptible of division into two separate questions for which different solutions were required. Each bound forward, whether long or short, demanded a certain definite signal policy. Each was preceded and followed by an intensive action which resembled more or less closely the battles of position, warfare. These questions may be considered separately, the latter being taken first, as it more closely resembles the problems of the preceding years.

The actions of August 8th and September 29th were both of them position battles on a scale that had never before been surpassed. There was, however, this difference from the battles of 1917. There was no comparison between the relative strength of the artillery engaged. From June, 1918, onwards, one of the most comforting aspects of the situation from the point of view of the forward troops, whether infantry, artillery, or engineers, was the fact that for every shell the enemy sent over he received ten or twenty back. In the bombardments which immediately preceded the great engagements of the summer and autumn of 1918, the British artillery dominated the situation to such an extent that the enemy retaliation was largely blind. Shooting by the map was the rule throughout. Even that was smothered to a very great extent by the accuracy of the fire of our own guns and the necessity he was under of keeping his heavy guns far back to avoid capture. This was the one factor which permitted of the survival of the slender ground or poled cable net-work which was the mainstay of the intercommunication system even in the most intense of the engagements subsequent to August 8th.

On this date, the attack was made on a great portion of the British front from a well-prepared defence line, part of the mechanism of which was an efficient and safe buried cable system. The success of the attack quickly carried the Divisions and the Corps off the buries however, and from that time onward, with one exception, the pauses were never of sufficient duration to permit of buries being dug. Indeed, the conditions were such that the expenditure of labour would not have been warranted. The main enemies of the line system in future — if common sense was exercised in choosing routes — were tanks, traffic and hurried movement.

The solitary exception occurred when a slight pause took place in and about the positions in front of the Hindenburg Line which had been occupied by British troops in the summer and winter of 1917. Here buries existed which had not been destroyed either by our own troops or by the Germans. Exploration of deep dug-outs and shafts revealed testboards and racks which gave promise that the buries might still be in a fair state of preservation. Area detachments were hastened up from their work of salving cables in the rear of the Army areas and pairs were tested out. In many cases, the buries enjoyed a brief and partial revival of use before the final and speedy success of the attack on September 29th took the Divisions in one stride across the Hindenburg Line and well into the unspoilt country beyond.

This very temporary and partial appearance was the last that was seen of buried cable until some months after the Armistice, when the salvage parties, having cleared the greater portion of the airline and cable above ground, commenced to carry out trials as to the possibility of recovering the thousands of miles of valuable wire which underlay the old battlefields. Although the buried system was eliminated as a characteristic of the forward signal system during an advance, yet line signalling still remained the main method employed. The principle of the single Divisional route was insisted upon and this normally consisted of three pairs of poled cable, usually of twisted " D8," which had by now proved itself to be the best of the twisted cables for use on long main trunks. These trunks were carried forward by cross country routes, avoiding valleys and other natural features likely to receive attention from the enemy's artillery as possible concentration points for the attacking troops. At or near a common Brigade headquarters the pairs were led into a dug-out or strong point which was fitted up as a forward communication centre, usually with one or two ten- line cordless exchanges and one four plus three buzzer unit. From here, short spurs ran to the headquarters of the neighbouring Brigades and to the artillery, though the latter sometimes ran a separate system for themselves. At the main Divisional headquarters there would be a more elaborate office which varied in complication according to the previous experience of the General Staff and the weight exercised by the wishes of the Divisional signal officer. With a slender exposed line system and the greatly increased maintenance burden which was its invariable corollary, it was to the latter's interest to decrease the subscribers on his exchanges to the greatest possible extent. According as he was assisted or hindered by his Staff in the attainment of this object, so his responsibilities decreased or increased. The available personnel was a constant factor in all Divisions and the resultant efficiency of the system therefore depended largely upon the attitude taken up by its users. One division went into action on September 29th with no less than 42 subscribers on the Divisional exchange. Forward of Division, the system was as described above, while six very insecure cable pairs extended rearwards through rear Divisional headquarters to the advanced Corps exchange. It is not surprising that great congestion and friction between departments competing for the use of the telephones reduced the efficiency of the Staff during the battle. It was only a typical case of a Division which had escaped the trials of the earlier portion of the year and was hurriedly adjusting itself with an ill grace to new conditions. The lesson was, however, learnt once for all and a reversion to the slender signal system of mobile warfare completely eliminated friction and ensured efficient control in all the battles which followed.

At Divisional headquarters, personnel and instruments for a second communication centre were held in reserve, and at the communication centre already established, a cable detachment waited to proceed forward immediately the enemy's resistance was overcome. When news of a forward movement was received, the detachment was ordered up to the site chosen for the next station and the forward office was transported either by car, box-car, lorry, or G.S. wagon. The method of transport employed depended upon the speed of the advance, the likelihood of a Divisional move, and the state of preservation of the forward roads. In any case, it was usually possible to establish the next office and connect it up with at least one cable pair and one earthed line, by the time the Brigade headquarters had taken up their new position. If possible, spurs were run by the linemen of the forward centre or by the cable detachment to the Brigade headquarters, but if time did not permit of this, the Brigade signal officer was expected to connect up his office to the new centre himself.

As the advance continued, the next stage of the proceedings would be the telescoping of the Divisional lines from the rear by the forward movement of Divisional headquarters. By this 'time the Corps was usually in a position either to take over the old Divisional exchange or to establish a forward Corps exchange in close proximity. Divisional "Q" was usually left here with a short cable spur to the Corps exchange and the whole of the Divisional signal personnel was thus able to proceed forward to the new headquarters, the lines behind the latter passing to the maintenance of the Corps.

It was essential to the most efficient carrying out of the policy outlined above, that the Divisional artillery headquarters should agree to modify the separate system which it had been their practice to maintain during stationary warfare. In the more intensive battles, where pauses of some duration took place, the D.A. headquarters exchange, with its radiating lines to its eight or nine artillery Brigades, was still desirable and possible, or, at the least, special artillery lines were included in the divisional trunk route, and separate artillery and infantry exchanges set up side by side at the forward communication centre. Once movement set in, however, the pooling of all the signal personnel in the Division on one route was the rule, if efficient service was to be given. This was generally recognized and in the more mobile periods the operators and linemen of the artillery headquarters signal section formed a valuable proportion of the personnel of the forward communication centres.

The building of the line system varied with the circumstances of the advance. The influence of enemy artillery was almost negligible except as regards the details of the routes followed. If the country were open, the choice lay between poled cable and ground cable, the latter being laid in ditches or in the open German cable trenches which seamed the country over which the troops were advancing. The former was erected sometimes on the black-and-white service poles, but more often upon rough poles taken from the German dumps or cut from local woods. At other places, the lines were run along the German permanent routes, one or two pairs being perhaps slung on the poles at sufficient height to be out of the way of tanks, and the other pair run as ground cable with the possibilities of damage localised by tying back the cable to every permanent pole. On yet other occasions, when the country became more enclosed, cable slung on hedges — familiar to everyone from practice and manoeuvre days in England — was rapidly laid and quite safe from traffic.

Three types of country had to be crossed during the advance. The devastated Somme area was an obstacle which confined the cable wagons to the crowded roads as in the retreat. The open country, which was perhaps typical in the Cambrai area, exposed the cable to danger from all varieties of traffic, but, on the other hand, permitted free passage for cable wagons in almost every direction. The network of hedges beyond the Sambre-Oise canal presented features alike in every respect to the more enclosed portions of the English countryside.

The methods employed varied with the country, but the outstanding feature of the advance was the free use made of the six-horsed cable wagon. Light cable carts did useful work in difficult country, man and horse-drawn barrows were used to cross the crater-pitted country of the old battlefields, but the six-horsed cable wagon was the main stay of the forward signal officer. The critics of the stationary warfare period were dumb before the reversion to type which now took place. On occasion, during the most speedy phase of the advance, energetic cable detachments carried their lines forward beyond company headquarters. The company commander's "D3," the battalion 4-plus-3 board, and the Brigade ten-line cordless, succeeded each other in the same office as the Divisions advanced, but before the latter arrived, the cable head was once more several miles ahead. On one occasion, at least, a cable detachment commander enquiring for the locality of the battalion headquarters, was obliged to ride back along the line for a hundred yards or so before he could locate British troops. He was then told that the village in which his wagon was awaiting his return was officially in the hands of the enemy and that the N.C.O. to whom he was speaking was in command of an outpost detachment.

Little trouble was experienced in these marvellous days from enemy shelling. There were, however, other menaces to the safety of the lines. As the scene of action was approached from Corps headquarters, one cause of interruption might be seen in the steady advance of the inflated kite balloons along the main roads. Held captive by their wire cables, the balloons travelled at a height of over a hundred feet and buried crossings were, of course, the only means by which the cable could be protected against them. Naturally, also, buried crossings were not the easiest things to achieve across metalled roads during a hurried advance. All poled or slung cables were cut and, often, the men of the kite balloon detachment were too occupied with their own affairs to make good the damage they had caused.

Further forward, damage by tanks was frequent, for more mobile conditions once more prevented efficient liaison with this arm. Not only were cables torn asunder, but the light airline routes of the Corps and even the shorter of the reconstructed permanent routes were often destroyed by tanks carrying fascines or supplies. Recommendation was made by sorely harassed signal officers that the height of the loads carried by the tanks should be decreased in order to prevent this constant interruption of signal communication.

Further forward, still, the presence of cavalry once more interfered with the Divisional routes, the experience of Cambrai being repeated on a larger scale. Large bodies of cavalry cannot cross country without destroying ground cables which lie in their path. Too often, they did not take the trouble to avoid or repair the poled cable which should have been safe from their attention. At the same time, it must be admitted that the inconvenience was not always one-sided Badly-slung cables are a menace to horsemen at night and, in the haste of the advance, forward cable routes were not always built at a height which carried them well clear of the head of a mounted man. More care was needed on both sides to produce a cavalry-proof system and to ensure its fair treatment when erected.

One source of damage to the lines which was mainly confined to open country was the ordinary Divisional traffic. In the Cambrai district, especially, the dry weather, the rolling open downs, and the persistent shelling of main traffic routes indulged in by the enemy, all combined to entice the limbers and G.S. wagons of the Divisional transport off the roads. Main cable routes were an obvious guide to cross-country traffic and were used continually for this purpose. In the daytime all went well and the advantage of a short cut was not counterbalanced by damage to the lines, but at night the tracks were widened at the expense of the poled cable that bounded them. Time after time linemen were sent out along the main Divisional route to find from a quarter to half a mile down in the dirt and barked and torn by the wheels of the transport wagons.

A last source of trouble which must be recorded was the wilful cutting or destruction of routes by parties of men not personally interested in their preservation. On a single Divisional front within one month, three such instances caused great trouble. On the first occasion, the night before the battle for the Hindenburg line, two or three hundred yards were cut out of a main Divisional route by a cavalry squadron to make a picket line for their horses. Occurring on a dark foggy night, the damage was not repaired for some two hours and during that time the Division was entirely cut off from all its Brigades. A few days later, a similar happening proved on investigation to have been caused by the infantry of the very Brigade whose lines had been cut, and the missing pieces of cable were found to have been used in the building of bivouacs. Finally, on the evening before the forcing of the Sambre-Oise canal, the whole of the poles from a Divisional route were removed by Australian troops and used for a similar purpose. Such incidents might well make the signal officer despair of human nature. They were far too common and showed a thoughtlessness which was inexcusable. Only by careful education of the rank and file of the Army can their repetition be prevented.

Forward of Brigade headquarters, the main route was sometimes, as has been said, carried forward by the Divisional cable detachment. Much more often, light lines were laid by the Brigade signal section to a forward communication centre of their own, which was later replaced by one of the Divisional centres. From this centre light routes, which were generally of "D2" or "D3" cable, were run to battalion headquarters. Here the line system normally stopped, communication beyond being by visual or runner, as in almost all previous engagements.

The chief lesson of the mobile warfare to the Brigade signal section was, perhaps, the need for some quicker method of laying cable than by man-power. The absence of the Brigade pack animals was severely felt and only by the greatest exertion could the line system be kept complete as far forward as battalion headquarters which were of course constantly upon the move. This was especially the case in heavily wired and enclosed country and the reports of Brigade signal officers testify to the need for more mobility in the transport of their section.

A natural consequence of the hurried movement of the advance was a difficulty in supplying forward units with cable. This had been anticipated and, when the advance commenced, nearly all units were well above establishment and had a considerable proportion of single cable. Artillery cable wagons were filled up and the Divisional ammunition column also usually carried a large supply of "D3" cable. Infantry brigades and battalions were well supplied with "D2" and battalions held in many cases their full establishment of enamelled wire, which, however, they were loath to use except in times of great scarcity. Orders were issued that all possible lines abandoned were to be salved, and the attachment of an area detachment to many Divisions helped them to carry out these instructions very thoroughly. At each pause in the operations, the greater part of No. I section of the Divisions was employed sedulously collecting cable from the district in which the section was billeted. Much British cable was lying about all over the country and much German cable of good quality was also available for the trouble of collecting it. The wise Divisional signal officer saw to it that he went into action each time with some 60 to 80 miles of cable, of which two-thirds was probably twisted and one-third single. He was thus enabled, if necessary, to pass over a signal system to a Division passing through his own Division without feeling the loss of the cable or having to exact for it a quid pro quo. He knew that in the few days of res t that would be permitted to him he could make good his losses. Thi s was especially the case if there happened to be an abandoned Corps heavy artillery headquarters in his immediate neighbourhood. The Corps H. A. section was so understaffed that it was impossible for them to do much salving. They were also in a better position to replenish their stores from Corps. The network of cable they had abandoned was invaluable to the Division. By means of utilizing all such sources and the occasional finding of a German dump, many Divisions went through the greater part of the advance in September and October without calling upon the Corps for large supplies of heavy cable, though supplies of "D2" and "D3" were always useful when they could be obtained.

Once again the question of laterals was of paramount importance for the co-ordination of both advance and battle action. The system built up before any of the great battles included, of course, both Division and Brigade laterals. These were run without difficulty by the cable detachments if sufficient notice was given and notification of the position of flank headquarters was provided by the General Staff.

The case of the Division next the French presented peculiar difficulties, for our allies were not believers in lateral lines between Divisional headquarters and would not trouble to run them. A wise disposition of the Corps in question, however, permitted of the use of the Corps cable section to lay the line from right to left which was normally the duty of the British Division. Little difficulty was then experienced in keeping touch with the French division on the other flank. It was not, however, always possible to use the line when completed. On more than one occasion a "diss" on the line was found to be due to the fact that the French operator had hung the line up on a convenient nail in the office with the intention of attaching it to an instrument only when his own Staff desired to speak to the British General Staff.

Brigade laterals were dispensed with when movement was at all speedy and even Divisional laterals were not always possible under the most mobile conditions. In such cases telegraphic communication with the flank Divisions could usually be obtained via the Corps system, but speaking over the long lines involved was usually out of the question.

The only alternative method of communication of vital importance in rear of battalion headquarters was wireless telegraphy. The main advance in the tactical use of wireless in Division and in Corps was the provision of sufficient extra stations to permit of a complete stepping-up system all along the main line of communication. An extra Wilson set at the Corps gave an advanced station which acted both in this way and as a transmitting station over unusually long distances. The issue of a fourth trench set to Divisions had a similar effect. The extra trench set was erected at the forward communication centre which was destined to become the new Divisional headquarters. The directing station at old Divisional headquarters continued to work until this set had taken over. It then dismantled and proceeded to the new headquarters, or, if movement was very rapid, proceeded straight forward to the next communication centre. In either case, it took over control when it again came into action. Forward of this, the Brigade trench sets — carried sometimes on stretchers, sometimes on pack ponies, sometimes on light Lewis Gun handcarts — served the Brigade centre or a common battalion headquarters. By judicious use of the five sets, wireless was always available, either as an auxiliary to line communication, or as an alternative when the lines lagged behind the general advance, as, in spite of all efforts, they sometimes did.

Forward of Brigade or battalion, as the case might be, the "Loop" sets were often in use up to ranges of 4,000 yards with considerable success. In actions which at all resembled the position warfare battles they were of great value between battalion and company headquarters and between batteries and observation posts. Their use varied in different Divisions, and in some they were scarcely employed at all, as visual and runner were found sufficient for the modicum of communication required within the battalion. Even so, however, they had almost completely ousted the power buzzer amplifier sets from favour and it is unlikely that even a return to trench warfare would have restored the latter more cumbersome instrument to its erstwhile popularity.

The use of wireless as an integral part of the Divisional chain of communication had entirely altered its relation to the line system and much closer touch was kept between the signal office and wireless office during the advance. The connection of the wireless station with the former by wire had become a sine qua non whenever the two offices were not in the same building or within easy reach of each other by orderly.

The traffic now dealt with by the wireless station was of the order of anything from 20 to 80 messages a day, and another effect of this great increase was again seen in the partial abrogation of the cipher restrictions. Clear messages were the rule in the mobile phases of the advance; whenever clear messages were forbidden, wireless traffic dropped at once to very low figures and the forward fullerphone and sounder lines were overloaded in consequence. Never was it so evident that the chief obstacle to the free use of this method of signalling was the strangle-hold exercised upon it by the need for insistence upon the use of cipher.

The ranges over which the sets worked were often towards the extreme limit of their power and the need of a more powerful set was felt in the Divisions as well as at the Corps. Locally, improvements were made in the Divisional wireless system by the use of continuous wave stations, but this could only be done at the expense of an already insufficient artillery wireless system. The solution of both the range and the jamming problems which have worried the Divisional wireless officer in the past would seem to lie in the direction of the adoption of continuous wave wireless for all purposes, but this was not possible before the Armistice put an end to the war in November, 1918.

A special development of continuous wave wireless which requires some mention was the use of the sets for "flash spotting" and for observation work generally. The general situation as regards cable did not permit of the lavish use of lines between observation post and batteries, and their place was largely taken either by "loop" sets or, more frequently, by continuous wave stations. Fleeting targets could not have been engaged to anything like the extent they were without the help of these sets and a large measure of the difference between the accuracy of the enemy and our own artillery fire must be attributed undoubtedly to the free use of wireless for observation purposes.

Artillery wireless was perhaps hampered more by lack of transport than by any other consideration. The transport of the artillery Brigade signal sub-sections was quite inadequate to their needs and many signal officers who had had no personal experience of the value of C.W. wireless were only too glad to leave their sets behind. In some Corps, an effort was made to provide extra transport for the wireless sets, but this could only be a partial solution of the difficulty, as the rough roads and unsprung vehicles played havoc with the delicate instruments.

Another departure in the use of wireless was its employment on a large scale with Divisional and Corps observers. For this purpose both spark and C.W. stations were employed. Detachments of Lovatt's Scouts and special Observation Sections had been organized in many Corps and Divisions and, while these parties relied on light lines and visual to a great extent, C.W. or spark wireless was a valued supplementary means of communication. Special sets with their complement of operators were allotted to the Observation Officers and very valuable reports were sent back. These were, indeed, often the only reliable situation reports which the higher command was able to obtain. Although the line system might be intact and the Divisional wireless chain working, these could only deal with messages if messages were sent to them. Too often, forward commanders were so obsessed with their own plans as to be unable to spare time to keep their superiors informed of the course of operations. It was at such times that the "Divisional Observation Officer" — the Divisional Commander's own "eyes" — was able to keep him informed through his special communication system of much that was essential to a correct appreciation of the situation.

In the summer, when the German long-distance bombing planes were particularly active, a special installation of continuous wave wireless stations had been arranged in connection with a night-flying R.A.F. squadron to assist in combating their activities. One station was established at the squadron headquarters and three outlying stations at selected anti-aircraft defence centres. These outlying stations sent in warnings to the squadron when the approach of hostile aircraft was detected.

The system worked well and was subsequently extended into Army areas. After the commencement of the Allied autumn offensive the enemy bombing of back areas declined considerably. It is an interesting sidelight on the opinion of the anti-aircraft officers on the value of wireless telegraphy as applied to their work that in many cases the sets that had been allotted to them temporarily for a specific purpose were later deliberately stolen and kept in use for general intercommunication purposes during the advance, for which no allotment of C.W. wireless stations had been authorized.

A still further example of the use of continuous wave wireless during: the advance was the establishment of eight or nine stations at important railroad junctions to assist in the handling and direction of railway traffic. The Railway Operating Division pronounced these stations to be invaluable. The sets and personnel were found from the equipment and staff of the Central Wireless School, and during their special employment were administered by the O.C. G.H.Q. Wireless Observation Group.

The old difficulties which attended the use of wireless were once again in evidence, but to a much less degree. Brigade Staffs still did not make as much use of this means of intercommunication as they might have done or as the situation warranted. Jamming both by German and by our own sets was very bad, and the poorly trained signalmen "A" with the artillery sets found themselves particularly badly hampered in this respect. Control was much improved, it is true, but with as many as 66 spark sets and 49 C.W. sets working on the ground in the main command system of a single Army — and numerous additional sets serving special needs — a certain amount of interference was inevitable. The German Army, also, relied upon wireless to a great extent for communication forward of Division and their sets added to the confused jumble of sounds from which the operators of individual stations had to select the signals of their own particular vis-d-vis.

With both these drawbacks, however, wireless was still of great use and often of vital importance, and the wireless establishments and the time spent on perfecting this method of signalling were absolutely vindicated by the experience of these last months of war.

With the consideration of the line system, and of the auxiliary wireless chain, the principal elements of the main communication system in rear of battalion headquarters have been passed under review. It was only during the initial stages of the fiercest attacks which involved a preparation period comparable in some slight degree to that of the 1917 battles, that other methods bulked at all largely between battalion and Divisional headquarters. Pigeons and - messenger dogs were used on occasion, but never regained their former importance in the signal scheme of operations. Their use, when they were employed, presented no special features of interest other than those already discussed in former chapters. The message-carrying rocket, also, was only occasionally used in those battles which were more of a set-piece nature, and, with them, disappeared also the many varieties of flashlight and rocket signals which had been the most picturesque feature of position warfare.

Motor cycle despatch riders and mounted orderlies were utilized to the same extent as in former mobile campaigns. During the fogs that characterized the early autumn mornings, they were often, though themselves much hampered, the only reliable means of communication to supplement the Divisional wireless stations. Visual on such occasions was impossible, and the maintenance and forward extension of the cables was also extremely difficult and very slow. Runners were, as ever, a reliable means of forward communication, but the use of visual increased at their expense in the comparatively shell-free battles of the advance between the German defence zones. A feature of the runner organization in one Division was the organization of a "chain" which was a much exaggerated form of the relay runner system, each man of the chain forming a post in himself and being in sight of the next "link."

Perhaps the most typical of all the message-carrying agencies of the advance was the mounted orderly, and in this respect the establishment of the Divisional signal company was still woefully inadequate. The deficiency was represented to the Divisional and Corps Staffs and was met in various ways, according to the sympathy with which the request for more mounted men was viewed. In some Divisions, officers' grooms and spare chargers were placed at the disposal of the signal officer. For small journeys between headquarters over easily recognizable tracks in clear weather these men were of use, but they were completely lost when it came to making use of a compass or picking up difficult landmarks from a study of the map. A much more efficient system prevalent in many formations was the attachment of a troop of Divisional mounted troops to the signal company, and often, when the whole of these men were required by the Divisional Commander, their place was well filled by a troop from a cavalry unit which happened to be operating with or near the Division. Finally, another measure by which the available orderlies were frequently increased was by the allotment of a section or platoon of Corps cyclists who did valuable work wherever machines could be ridden.

The use of the aeroplane as a despatch carrier was inaugurated in at least one Corps, and aeroplanes were used considerably over the whole front for the collection of reports of the situation as seen from the air. Popham panels were available at Division and Brigade headquarters but were seldom employed, the "aeroplane dropping stations," the establishment of which had by now become part of the usual routine of Divisional signals, being used almost entirely for the dropping of messages from the planes. Much valuable information was passed back in this way and the calling of the Klaxon horn will recall the days of the advance to all ranks who spent any large portion of their time at or near Divisional headquarters.

Men to man the dropping stations were often lent from the Divisional pioneer battalion, and in more than one way the signal section of this battalion had been of the greatest use to the Divisional signal company commander. His resources had already been strengthened by the addition of No. 5 section to the company. In most Divisions the machine-gun signal system had been done away with as a separate system and most of the new section absorbed into the general communication scheme. The pioneer battalion, also, could do without much intercommunication and usually the O.C. battalion was quite ready to fall in with the suggestion that men should be drawn from his signalling section to assist in the Divisional visual chain. It was, indeed, only by means of these men and some of the best visual signallers of the Brigade pool that it was possible to build up anything like an efficient visual system. To the pioneer battalion signallers, themselves, the Signal Service is indebted for very loyal and very efficient service, and whether in charge of the aeroplane dropping station, salving and repairing cable, or engaged upon the more technical work of manning the Divisional terminal or transmitting visual stations, their work was invariably carried out conscientiously and cheerfully.

Visual was again much hampered by the mist and smoke. These decreased visibility in the early morning attacks to such a degree that the whole army was reduced to groping its way forward blindly, keeping direction merely by the aid of the shriek of shells passing overhead, the crash of the barrage on the enemy's lines, and the roar of their own guns behind them. Alternative visual was established in most Divisions, but it is rather questionable if the expenditure of men was always justified by results. It was another case of preparing for the worst. If the lines and wireless were both out of action, visual was of the greatest value. Under the circumstances of the advance, however, it was only through bad organization or quite unusually unfavourable conditions that the visual chain became essential in rear of Brigade headquarters. Even when such cases did occur, it was quite likely that the weather conditions would not permit of visual being employed.

Forward of Brigade headquarters, visual was useful: forward of battalion headquarters it was essential, but no special features of interest marked its use. The conditions were not nearly so exacting as in the position battles and every type of instrument could be used at one time or another without untoward results. The Lucas lamp was an easy favourite, and after this in popularity came the 1918 patterns of disc and shutter. Heliographs could have been much used had more been available, but they were not essential over the short distances which separated the reconnoitring detachments from company or battalion headquarters. Visual was much more used by battery signallers, also, and all observation work was done by this means when cable was short and wireless sets not available. A departure in the tactical employment of visual in the Division was the appointment of an officer especially to control the visual stations. It was found that N.C.O.'s did not usually possess enough initiative and skill to select the best sites, or authority to co-ordinate the Divisional and Brigade schemes. Where a visual officer was definitely appointed the best results were invariably obtained.

The signal system of the cavalry does not call for any particular comment as regards the means employed. Lines were used during the concentrations behind the infantry Divisions; wireless, visual, and orderlies were predominant, when the cavalry Brigades were working in front of the dismounted troops. Great use was made of the Divisional lines by the officers in command of the cavalry reconnoitring parties who were feeling their way forward in pursuit of the swiftly retreating enemy. In general, a separate line system was not attempted on a grand scale, when the cavalry were operating as an independent force or as individual Brigades attached to the Divisions in the line. The light motor and pack wireless sets proved as efficient as usual, and these and motor cyclists amply sufficed for cavalry Division-Brigade communication while on the move.

The chief lessons that can be drawn from the cavalry action of the advance was the efficiency of the Cavalry Wireless Squadron which had taken the place of the wireless troops of the cavalry Divisional Signal Squadron. All the arguments in favour of the use of wireless in mobile warfare with infantry are, of course, redoubled in the case of cavalry action. As soon as wireless became a practical proposition for Army use, it was quite evident that the direction in which it must first replace lines was with a swiftly-moving force like the Cavalry Corps. This was shown clearly in the mobile warfare of 1914, and the cavalry signal establishments were altered accordingly. The appointment of an A.D. Signals, Cavalry Corps, kept cavalry signals on an equal footing with those of the infantry Corps, but with this exception the signal squadron headquarters — though slightly strengthened — had not been materially altered. The 1914 and 1918 cavalry signal establishments are shown in detail in Appendix I

The mobile warfare, the principal features of the signal practice of which have just been described, continued with accelerating speed until the signing of the Armistice on November nth brought the war to an end. No particular features arose during the last few days of hurried advance to change the characteristics of the line or wireless system. The Signal Service had adapted itself thoroughly to this fresh type of warfare which was much more in keeping with the temperament of the personnel of the forward signal units. Everybody was working at highest pressure, but all were doing their share cheerfully and ever with an eye to giving a helping hand in other directions than their normal work. This was the day of the forward detachments of the Brigade and Divisional signal units. The men of No. i section of the Divisional signal companies, especially, with the memory of the seemingly endless days spent on the buried cable systems of 1916 and 1917, were enthusiastic in the performance of work which they felt was more what they joined the Army to do. These last few days in the van of a victorious Army repaid the cable detachments for all the drudgery of the preceding years. Their days were enlivened by the capture of enemy signal apparatus of every description; by long trips on horseback or on motor cycles reconnoitring abandoned German telegraph routes; even, on occasion, by the opportunity of chalking their unit's name as the first discoverers of abandoned German guns and howitzers. One obvious deficiency in the mobile equipment of the Divisional signal company was remedied by the illicit absorption of German field cookers which added much to the comfort of the forward detachments in the last week or two of the war, and of the whole company after the Armistice. The officers of the Divisional Signal Company, also, were employed in turn on the congenial work of reconnoitring forward along the roads for good cable routes, and searching captured towns for abandoned apparatus and signal offices. Occasional machine-gun, or rifle fire was very little heeded in the absence of shells, which made the war of the last few days utterly unlike anything that had gone before.

No difficulty was experienced in keeping the Divisional system well in front of the demands of Brigadiers. The deciding factor in the speed of the advance was supply and transport, and not signals. The signal companies could meet all demands upon them with a little in hand, and when the advance came to an end well beyond the Belgian frontier, it needed only a few finishing touches to connect up to the Army, Corps and Divisional system everyone who desired, and had any right to a telephone.

Footnotes

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Chapter XV