Part 2

In order to assess at their true worth the achievements of the Signal Corps during the war, it is essential to realize the amazing number, variety, and magnitude of the tasks the corps was called upon to perform. The Signal Corps is a staff department charged with providing means of communication for the army, both at home and overseas. According to the present tables of organization, one field signal battalion is usually attached to each division, the telegraph battalions being used as corps or army troops. Generally speaking, the telegraph battalion maintains communications in the rear; the field battalion usually operates with the combat troops at the front. In addition to these troops, there are numerous special units, such as pigeon companies, radio companies, photographic and meteorological sections, which are attached to corps, armies, or to General Headquarters. In France where hundreds of miles separated our base ports from our troops on the firing-line, there devolved upon the Signal Corps an enormous amount of work in the area known as the Services of Supply. The magnitude of the telegraph and telephone systems in the S. O. S. is illustrated by the fact that when the Armistice was signed, the Signal Corps in France was operating 96,000 miles of circuits known as “long lines,” with 282 telephone-exchanges, and a total of nearly 9,000 stations. The requirements for wire in the field were even greater. When our operations were at their height in the summer of 1918, it was estimated that the Signal Corps would require 68,000 miles of “outpost wire” a month for use at the front in connecting telegraph and telephone systems. Outpost wire is, I ought to explain, a development of the war. It is composed of seven fine wires, four of them bronze and three of them of hard carbon steel, stranded together and coated first with rubber, then with cotton yarn, and finally paraffined. This wire is produced in six colors—red, yellow, green, brown, black, and gray—in order that it may readily be identified in the field, the red wire running, for example, to the artillery, the yellow to regimental headquarters, green to brigade headquarters, and so on. The enormous amount of this wire required is explained by the fact that very little of it was saved, it being out of the question to pick it up during the hurry and excitement of an advance, while hundreds of miles of it were destroyed during the heavy bombardments which usually preceded an attack.

Within the memory of many of us the size of combat armies was largely determined by the efficiency and scope of their signal systems, it being essential that the forces in the field should be kept within a size which permitted of communication being maintained between all units by means of runners, riders, or visual signals. Those were the days when messengers, often chosen by lot, crawled through the enemy’s lines at night in order to bring reinforcements to beleaguered garrisons; when stories of ambush and massacre or urgent appeals for ammunition and food were brought to headquarters by weary riders clinging to the manes of reeking ponies; or when, in the Indian country, cavalry columns communicated with each other by means of heliograph messages flashed from mountain-top to mountain-top, or signal-fires curling slowly skyward.

But all this changed with the introduction of the telegraph and the telephone, the communications of an army thereafter being limited only by the amount of its wire. A far greater change came, however, with the introduction of the radio or wireless, whose area of operations is limited only by the power of the sending apparatus. Now it should be kept in mind that each of the systems of military signalling which I have already enumerated—telegraphs, telephones, radios, panels, lamps, flags, pigeons, runners, dogs, and the rest—is an adjunct to the others—when one fails, another is employed to get the message through. If the wires of the field telegraph and telephone are cut by a barrage, the radio is employed; if a shell knocks out the radio set, the message is intrusted to a pigeon; should the pigeon fail, a runner attempts to take it through; and if the runner is killed, the message can be communicated, either by means of rockets or by cloth panels spread upon the ground, to the aviators circling overhead.

Despite the new methods of transmitting messages produced by the war, the telephone remains the backbone of the military signal system. Though the portable telephone instrument used by all front-line troops was manufactured in the United States for commercial purposes prior to the war, the switchboard in most general use by mobile troops was originally developed by the French, being the only telephone equipment used by the American forces which was not of American design. This switchboard, which was built in units so that it could be expanded from four to twelve lines, was the “Central” of the front-line dugout, being so compact that it could be carried as part of the equipment of a soldier and quickly put into operation. For the use of the larger field units there was designed a camp switchboard, with provision for forty wires, which when in transit resembled a commercial traveller’s sample-trunk. A third type of switchboard, for use at headquarters in the zone of combat, but where extreme portability was not essential, was designed in units, like a certain popular style of sectional bookcase, and could readily be increased to any size required. An important auxiliary to the field-telephone lines was the buzzerphone, an American device for use where extraordinary secrecy was imperative, it being impossible for the German Listening-in Service to eavesdrop on messages sent by this method.

[Illustration: COMMUNICATION BY USE OF PANELS.

When other means of communication is found impracticable, the infantry can communicate with aviators by means of panels of cloth cut in various shapes spread upon the ground.

_Photograph by Signal Corps, U. S. A._]

[Illustration: A MEMBER OF THE SIGNAL CORPS SENDING MESSAGES BY MEANS OF A LAMP.]

Prior to the war the “lance-pole” was used exclusively by American troops in the field, as it permitted of rapid line construction and served its purpose admirably in open warfare. The conditions prevailing in Europe made the use of this pole impracticable, however, and where poles were used at all they consisted of very short stakes with special cross-arms, miniature copies, in fact, of the commercial equipment commonly used in the United States. The enormous mileage of the trench-lines called for vast quantities of insulators, cross-arms, and other special fittings, in all of which there was great wastage, for though the instruments used on the military lines usually had a certain degree of protection, the lines themselves were constantly exposed to artillery and airplane bombardment.

A factor which greatly complicated the supply of the front-line forces with wire was the necessity for maintaining two-way or twisted-pair lines in order to avoid giving information to the enemy, for the detectors used in the German listening-posts were so highly developed that a telegraph or telephone message sent over a “grounded” or single-conductor line was to all intents and purposes sent direct to Berlin. This necessity for a double-conductor line relegated the old field-wire of open warfare to the scrap-heap, a long series of experiments being required to produce a twisted-pair wire which was light enough to permit of easy portability and rapid laying, strong enough to stand the strain of heavy traffic and shell-shock, and withal so well insulated that “leaks” to the ground might not reveal to the enemy listeners-in facts intended to be strictly confidential. The enormous demands for all types of wire and cables which came both from the A. E. F. and from our allies necessitated the United States being combed for every foot of available material and the speeding up of production until every wire-mill in America was working twenty-four hours a day. Yet, in spite of labor troubles, housing problems, and the difficulties of obtaining material and transportation, the wire-makers at home filled every requirement of the soldiers overseas.

Of all the varied activities of the Signal Corps, none was more fascinating or mysterious in its operation than the work of the Radio Intelligence Sections, particularly the so-called listening-stations, which, by means of supersensitive receiving and amplifying instruments electrically connected with ground-plates placed as close as possible to the enemy positions, were enabled to overhear the ground-telegraph operations of the Germans and the conversation leaking from defective or non-metallic telephone and telegraph circuits. This remarkable service, some of whose achievements would seem to the layman to verge on the miraculous, combined the discoveries of Ohm, Volta, and Galvani with the methods of LeCoq and Sherlock Holmes. These stations could, of course, operate successfully only under favorable conditions, the chief requisites being that the enemy’s trenches should not be too far away and that the intervening terrain should be free of creeks, gullies, or other features which might sidetrack the currents which it was desired to intercept. The listening-stations were usually situated in the second line of trenches, the ground-plates being placed about 300 yards apart. In order to obtain satisfactory results it was necessary that the ground-plates should be placed as close to the enemy as possible, the work of installing them, almost under the noses of the Huns, being one of the most hazardous duties which the signal troops were called upon to perform. The men operating the listening-stations had to remain on duty for a week at a time—a considerably longer tour of duty than was required, under ordinary conditions, of the infantrymen. They were expected to possess a fluent knowledge of German and to be able to both speak and understand it as well as they did English, though this requirement was not always fulfilled toward the end. They were thoroughly coached, moreover, in German military phrases and colloquialisms and had to be proficient in recording ground-telegraphy code, which, though slow, is extremely difficult to master. It will be seen, therefore, that the Listening-In Service demanded of its operators continuous interest and constant vigilance, together with a sufficiently active imagination to enable them to piece together the broken or garbled fragments of messages which their instruments might pick up, and to deduce from these messages what the enemy was doing or what he intended to do. Listening-in was very far from being a one-sided game, however, for the Germans, who were thoroughly conversant with its possibilities and limitations, maintained a service which was nearly, if not fully, equal to our own. The real superiority of our service lay, not in its equipment, but in the boyish enthusiasm of its personnel, many of whom were university undergraduates when the war began. With them the work never assumed the aspect of a daily task which had to be performed whether they liked it or not: they regarded it rather as a game, interesting, fascinating, exciting. The quickness with which they grasped the technicalities of the service was amazing. I knew of one case where a soldier of a Listening-In Section, wholly without previous experience in the work, overhearing a telephone conversation in the enemy’s lines which indicated that the watches in that sector were being synchronized, deduced that a raid on the American trenches was being planned. He promptly acquainted the divisional intelligence officer with his conclusions, and when the Germans launched their attack, expecting to take the _verdamte_ Yankees completely by surprise, they were greeted by a burst of rifle and machine-gun fire which almost annihilated them. After the moving warfare began it was, of course, extremely difficult to maintain these listening-stations, but when the advance halted, even for a night, listening-stations were always established if conditions permitted.

A far-fetched but, as it proved, entirely correct deduction was made by the operator of a listening-post whose curiosity was aroused by the sudden change in the nature of the conversation taking place over the enemy’s lines, familiarity interspersed with profanity abruptly giving way to studied politeness. From this he reasoned that a new division had moved in during the night. Prisoners captured the next day verified his deduction. Just before the St. Mihiel offensive one of our operators noted that the telephone conversations between the enemy units opposite his station had almost ceased, presumably because a troop movement was in progress which they did not dare to discuss for fear of being overheard, the truth being that the Germans were quietly withdrawing. Though he had practically no conversation to guide him, this by no means discouraged the American listener, who, by comparing the intensity of the T. P. S. (_telegraphie par sol_) signals he overheard, deduced with amazing accuracy the movements of the retiring troops. In comparison with such feats of deduction, Sherlock Holmes’s ability to deduce a stranger’s occupation from the condition of his finger-nails or the soles of his boots seems absurdly commonplace, doesn’t it?

A youth in search of excitement beyond that usually provided by battle could always find it by joining the Listening-In Service. In March, 1918, the American troops holding a certain sector were suddenly ordered to retire to a second line of resistance, but through an oversight the orders for withdrawal were not passed on to the Signal Corps men who were operating the listening-stations out in front. Serenely unconscious, therefore, of the fact that their comrades had fallen back and that German raiding-parties were prowling all about them in the darkness, they remained at their post throughout the night. It was not until the American infantry reoccupied their original position in the morning that the men in the listening-station learned that for eight hours they had been the only occupants of the sector.

While crawling over No Man’s Land to repair a break in a line connecting his station with a ground-plate, a Signal Corps man discovered a wire leading straight toward the enemy’s position. Being of an inquiring turn of mind, he followed it up on hands and knees until he actually penetrated the German trenches, where he made the interesting discovery that the enemy’s listening-station had tapped the same ground which we were using. Needless to say, he lost no time in crawling back and changing his ground-plates. This feat was paralleled by a soldier who followed an American raid into the German trenches, and, unobserved during the excitement, succeeded in attaching a wire to one of their ground-plates which was well within their lines, and, therefore, presumably in no danger of being tampered with. By this means he listened-in on the enemy’s conversations for several days before his wire was discovered and cut.

Though the work of the Radio-Intercept and Goniometric Direction-Finding stations lacked in some measure the danger connected with that of the ground listening-posts, it nevertheless provided many interesting incidents in the life of the Signal Corps man. The function of radio-intercept stations is, as their name implies, the interception of enemy radio messages. Goniometric stations are used, on the other hand, for locating enemy radio-stations, the work being carried on on much the same principles as flash-ranging, which I have described at some length in another chapter. By placing a goniometer—an instrument for measuring angles—at each end of a base line of known length, it is a comparatively simple matter to ascertain the angle of direction of an enemy radio-station, and, by prolonging the lines of these angles until they intersect, the location of the station can be approximately determined. That done, the information was sent to the artillery, which proceeded to sweep the vicinity in which the radio-station was known to be with a hurricane of shell. So highly was this system of radio detection developed that, after the salient at St. Mihiel had been cleared of Germans, every radio-station which our Goniometric Service had located previous to the attack was verified, the greatest error in location being approximately 500 yards. In many cases some of the German wireless equipment was still in the dugouts, and much interesting printed matter was picked up. This was the first corroboration of the effectiveness of our Radio Intelligence work.

Just as the naturalists can reconstruct from a few bones a prehistoric monster which they have never seen, so the goniometric experts are able to gain an amazingly accurate idea of the organization of an army by locating its radio-stations, for the lines of radio communication which spread fan-wise from army headquarters form a sort of skeleton, as it were, of the army’s organization, the location of the various stations and their distance from headquarters indicating quite accurately the position of the corps, divisions, brigades, regiments, and battalions. This fact was, of course, as well known to the Germans as to ourselves, and consequently extraordinary precautions were taken to prevent the stations from being located. Such a system of communications is known in military parlance as a “net,” that serving an army being called an “army net” and that of a corps a “corps net.” Just before the American offensive was launched at St. Mihiel a false corps net was set up considerably to the east of the point selected for the attack, this net being operated in as close imitation as possible of the real thing. Thousands of faked messages were sent in code, precisely as though the movements of an army corps depended upon them, and, to add to the verisimilitude of the proceeding, they were strongly seasoned with the profane and violent English with which American radio operators are accustomed to interlard their conversations. The German goniometric operators promptly located this network of radio-stations, and as the messages which were being transmitted appeared to be perfectly genuine, they naturally concluded that they had discovered the unsuspected presence of an American army corps, whereupon the German High Command took steps to move its reserves to the area which apparently was threatened. There is no means of knowing how effective this ingenious stratagem really proved, but the best answer would seem to be the surprisingly slight resistance which we encountered at St. Mihiel.

The operation of the mobile radio-stations which accompanied the smaller infantry units was always a most hazardous and trying business, requiring not only courage but a very high degree of resourcefulness and self-possession. In one case that I know of a Signal Corps unit received orders to have a trench radio-station installed at a certain exposed point by a certain time. They followed their instructions to the letter, but when their instruments were set up and they were ready for business, they discovered, to their extreme annoyance, that the infantry which was scheduled to occupy the position had failed to materialize and that they and their radio set were well in advance of our lines. From their position in a shell-hole they called up the regimental commander, reported that they were located according to instructions, and inquired what they were expected to do. Whereupon the infantry lost no time in moving up and occupying the position which, as the signalers mockingly asserted, they had been holding for them.

The exigencies of the Great War wrought many strange and startling transformations. Scientists who had devoted their entire lives to discovering methods for prolonging life turned their genius to finding new and effective ways of taking it; the tractor of the Western wheat-fields became the tank of the battle-fields in Flanders; the machinery and chemicals used for the manufacture of dyestuffs were converted to the manufacture of poisonous gases—and the dove became the army carrier-pigeon, bearing, instead of the olive-branch of peace, messages of battle. Though I find that many Americans seem to be under the impression that pigeons were unreliable and comparatively little used, they were, as a matter of fact, the most trustworthy of all the systems of message transmission employed by the fighting armies. When everything else failed, when the wires of the field telegraph and telephone had been destroyed by the German shell-storms, when the radio installations had been demolished, when the runners had been killed and the aviators driven back by the air-barrages, it was the pigeons which took the messages through. The official accounts of their exploits read like the wildest fiction. Over 500 birds were used by our troops in the St. Mihiel offensive alone. Through the messages brought by pigeons, American Headquarters learned of the whereabout of Major Whittlesey and his “Lost Battalion.” How trustworthy were these winged messengers is proved by the carefully kept records of the Allied Armies, which show that of the thousands of messages intrusted to pigeons during the four years of the war, _96 per cent were delivered_.

The use of pigeons as messengers is as old as recorded history, the Chinese, Egyptians, Greeks, and Romans all having used birds for this purpose. Word of the victory at Waterloo was brought to England by pigeons, and pigeons carried from New York to Washington the news that Napoleon had signed the treaty which added Louisiana to the Union. Among the oldest and most successful pigeon-trainers are the Belgians, many of the best flying strains used by the French, British, and American armies having been developed from Belgian stock. When the Hunnish hordes swept across Belgium, one of their first measures was to confiscate or kill all pigeons. For a Belgian to have in his possession a carrier-pigeon was for him to risk a court martial and death before a firing-party. Many of the pigeons taken from the Belgians were sent back to Germany for breeding purposes, producing birds which served against their former masters, but when the Americans established their watch on the Rhine, they ordered the immediate release of all pigeons in the area of occupation, thus giving thousands of feathered exiles a chance to fly back to their old homes in Flanders.