Aug. 1914 found the Expeditionary Force equipped with a signal service controlled by a director of signals on the general staff at G.H.Q. This service included a signal unit at G.H.Q., a lines-of- comraunication signal company, and a signal company with each corps and each division. Artillery intercommunication was, how- ever, entirely a separate matter for which that arm itself was solely responsible. So also, was intercommunication inside the infantry unit; and the absence of a chain of command within the signal service itself (each unit commander being responsible only to his own general staff) caused a looseness of organization which soon showed itself to be a grave defect. The means of intercom- munication employed were those already mentioned, viz., tele- graph, telephone, flag, lamp and heliograph, with the addition of wireless telegraphy, which was, however, at this time adopted only for the special requirements of the far-ranging cavalry divi- sion, and consisted only of one lorry and a few wagon and pack stations, all of rotary spark type. (The power of the stations was 3, 1-5, and 0-5 K.W. respectively; the range, when working to stations of similar type, 100, 80 and 30 miles.)
The signal organization summarized above proved adequate to deal with the mobile conditions of the first few months of the war. These early days were specially notable for the triumph of the motor cyclist. Telegraph and telephone, visual and orderlies, and mounted liaison officers also played useful parts, and it was not until position warfare set in in the winter of 1914-5 that fur- ther changes were found to be required. Then, however, the desire for, and the possibility of collecting, a greater quantity of more exact information (especially for artillery observation) led to a considerable increase in the complexity of the army signal organization. To the exigencies of position warfare may be attrib- uted almost all the evolution in signal implements and signal organization which marked the course of the war. The chief alteration in signal policy, on the other hand, was brought about not so much by position warfare as by the resumption of semi- mobile and mobile warfare which took place to a slight degree in 1916, toa slightly greater extent in 1917, and completely in 1918.
The principal result of " stabilization " was naturally an im- mense increase in the number and weight of the guns employed. Both for offensive and defensive purposes massed artillery be- came the weapon of paramount importance, and this had two principal effects on the forward signal service. The fire of the large number of guns employed could not be effectively directed without a greater measure of intercommunication; while at the same time, intercommunication in the region subject to heavy gunfire became more and more precarious.
The extra intercommunication required was supplied by a rapid increase in the number of telephones in use at observation posts and at artillery headquarters. The need for intimate liaison between infantry and guns led to a similar increase at infantry headquarters.
The magneto telephone came into use for the first time forward of corps headquarters, and, once the superior convenience and efficiency of the instrument were recognized, the demands for its installation increased so rapidly as to tax the signal service to its uttermost capacity. A new danger at once arose and threatened to wreck the whole intercommunication service. The tendency was to concentrate all available energies on the installation of telephones and the laying and maintenance of telephone lines. All other means of signalling lost their proper proportion, and an inefficient telephone service was soon in a fair way to become the only means of intercommunication throughout the whole army. Such an undesirable result was only prevented by the incidental troubles arising from the indiscriminate laying of lines. In effect, it was the " overhearing " menace, which will be referred to later, that, together with the prevalence of induction trouble and the difficulty of making " safe " the forward lines, proved to the signal service and to the commanders it served that it was unwise to stake everything upon one method of intercommunication.
The difficulty of maintenance of forward intercommunication was overcome partly by the adoption first of shallow and subse- quently of deep buried cable; partly by the evolution of various new alternative methods of signalling; partly by the perfection
and adaptation of methods which had temporarily fallen into disrepute under the new conditions.
In 1915, cables were buried 2 or 3 ft. deep and by this means temporary immunity from shellfire was gained; in 1916, the general adoption of the 6-ft. bury (while it saddled the signal service with endless labour problems) successfully solved the difficulty of the maintenance of an efficient forward telephone and telegraph system. One inevitable consequence of the adoption of the " bury " was the concentration of the forward lines into a few main routes, thus paving the way for the great reform in policy which was later brought about under the pressure of rather different circumstances.
The induction which resulted from the collection of 20 to 100 circuits in these main corps and divisional routes was reduced to a slight extent by the general substitution of the sounder for the vibrator in forward units 1 and by the elimination of the buzzer as a general means of intercommunication. It was later almost entirely overcome by the adoption of metallic circuits of twisted cable 2 for all forward lines.
Mention should be made of the alternative methods of sig- nalling which underwent their first main period of evolution in 1915. In 1914, the weight and accuracy of modern artillery fire had caused visual signalling to fall into disrepute as being too dangerous. It was soon found, however, that the lines which were at that time the only general alternative to forward visual signalling, were also untrustworthy, and that salvation lay in employing as many alternative means as possible and therefore in improving all available methods as well as evolving new ones. Visual was rehabilitated by the invention of the inconspicuous signalling disc and shutter, by the general adoption of " D.D. D.D." working (signalling from front to rear without reply) and by the adoption of the efficient electric signalling lamp in place of the more conspicuous and noisy Begbie oil lamp which was the standard equipment at the outbreak of war. At the same time the use of pigeons as message-carrying agencies was revived, and wireless telegraphy began to be adapted to forward work. The former were first used by the Intelligence Corps towards the end of 1914, when the British were operating in a district noted for its pigeon fanciers. From this small beginning grew a service which at the Armistice numbered over 20,000 pigeons, while no less than 90,000 men of all arms had been trained to handle the birds. Lofts were kept usually on a line passing about through divisional- headquarters and pigeons were forwarded by motor cyclist and taken into the trenches by selected pigeoneers. Here they remained until required for use or until 48 hours had elapsed, when they were released with or without messages.
Wireless telegraphy for the forward area was first attempted in the summer of 1915, when experiments were carried out which resulted in the standardization of two types of set, the I2o-watt (Wilson) and the $o-watt (British field) set. The former was intended for work at divisional and corps headquarters and consisted of separate transmitting and receiving apparatus. The spark transmitter received its energy from a 26-volt accumulator through a small motor-driven interrupter fitted in the set itself; its original complement was a crystal receiver specially designed for the short waves (350, 450, and 550 metres) on which the for- ward sets were obliged to work. The 5o-watt set, on the other hand, was a combined transmitter and receiver, the transmitting
1 The two telegraph instruments, the sounder and the vibrator, are worked on entirely different principles. In the former case the currents used rise to their full value very rapidly and then remain steady a comparatively long time. On the vibrator system, on the other hand, the currents used are constantly altering in value and even changing in direction, the vibrations being at an audible rate of frequency (several hundred per second). It is these latter rapidly alternating currents which set up rapidly alternating EMF in the earth surrounding the conductor and provide the ideal conditions for overhearing at a considerable distance. A buzzer is a particular type of instrument using " vibrating " or " alternating " current.
2 In a telegraph circuit consisting of two wires laid side by side, the electromotive force set up around one conductor will be neu- tralized by that set up around the other in which the current is travelling in the opposite direction. The most efficient disposition of such neutralizing cables is naturally that where the two halves are most intimately interturned, as in twisted cable.
