II
“ESSAYONS”
If, the next time you meet an officer of Engineers, you will observe his uniform closely, you will perceive that the buttons of his tunic, instead of being embossed with the arms of the United States, like all other branches of the service, bear a device consisting of an eagle, a castle, a rising sun, and the motto “Essayons.” Like the bow of black velvet, called a “flash,” which the Royal Welsh Fusiliers have sewn at the back of their collars to commemorate the fact that they were the last regiment in the British Army to wear the pigtail, so the buttons of the Engineers serve to remind their wearers that the famous organization is as old as the nation, tracing its history back to the Corps of Artillerists and Engineers of the Continental Army.
“Essayons”—“Let us try.” One likes the quiet confidence of the motto.
“Can you make roads for my guns through the swamps of the Wilderness?” asked Grant.
“Let us try,” replied the Engineers—and the roads were built.
“Can you build docks for disembarking ten thousand men a day and railways to carry those men to the front?” asked Pershing.
“Let us try,” the Engineers responded—and almost overnight miles of docks and networks of rails appeared as though at the wave of a magician’s wand.
“Can you locate the enemy’s guns by their sound? Can you keep our troops supplied with water? Can you print maps? Can you make dugouts? Can you operate search-lights? Can you dredge harbors for the entrance of our transports? Can you build highways and keep them in repair? Can you quarry the stone for those highways? Can you cut a million feet of lumber a day? Can you design better types of armored cars, sound-detectors, mobile cranes, portable sawmills, listening apparatus, mapping cameras, steel bridges, barbed-wire entanglements, than any in existence? And, if the necessity arises, can you fight?”
“Essayons,” answered the Engineers—whereupon all these things were done.
Whenever the army has had work to be done which no one else knew how to do, they have sent for the Engineers. Who designed, built, and operated our tanks before the organization of the Tank Corps? The Engineers. Who organized the Gas and Flame Regiment? The Engineers. The Camouflage Corps? The Engineers, of course. Who did the mining, quarrying, timber-cutting, well-driving, dock, bridge, road, railway, and camp building for our armies overseas? Again, the Engineers. Indeed, I doubt if any organization of any army in the Great War can show such a record of varied activities and successful accomplishments as the Corps of Engineers. One can say of the American Engineer, as Kipling said of the British Marine:
The immense importance attached to the work of the Engineers is strikingly illustrated by the fact that, whereas the army was increased to 19½ times its pre-war size, the enormous problems of field fortification, construction, and transportation, both with and behind the fighting forces, as well as the direction of many entirely new phases of warfare, necessitated an increase of the Corps of Engineers to 131½ times its strength at the beginning of the war. Prior to July, 1916, the corps consisted of only three battalions, with a total strength of not over 1,900 men, but when the Armistice was signed there had been organized, or were in process of organization, 500 Engineer units, with a strength of some 312,000 men, or more than 10 per cent of the entire army.
Now it must be kept in mind that in the original corps of pre-war days the men were trained only as sappers and not in the countless specialist branches which were developed by the great conflict. The fundamental use of sapper troops is, theoretically, at least, the supervision of technical work during tactical operations. One regiment of sappers is normally assigned to each division, is under the immediate command of the divisional commander, and operates as directed by him. To this regiment is given the work of organizing positions for defense, which includes the construction of trenches, gun-positions, ammunition-dumps, and dugouts, the repair and maintenance of roads in the divisional area, the construction of shelters where required, and the general direction of the work necessary to keep open the lines of communication and supply. In open warfare it is customary for the divisional commander to hold his sapper regiment in reserve to be used for applying the decisive pressure or resistance at the moment when it is most needed. When going forward with the infantry, sapper troops usually have a definite technical mission, such as the organization of captured ground, the destruction of obstacles and the bridging of streams. During a retreat they are attached to the rear-guard, being charged with the demolition of bridges, the obstruction of roads, and the cutting of railway communications. Though the ranks of the Engineers were filled, for the most part, with men who were experts and specialists in certain trades and professions, they were time after time thrown into the line as combat troops, fighting shoulder to shoulder with the infantry. On more than one occasion they showed that, destitute of combat training though many of them were, they could handle a rifle or a machine-gun as well as an axe or a spade. At Cambrai the 11th (railway) Engineers, caught in the German counter-push, offered a stubborn and heroic resistance against overwhelming numbers. At Amiens another railway regiment, the 11th Engineers, formed a part of the little force with which General Sandeman Carey blocked the gap in the British line and thereby prevented the Germans from breaking through to the Channel ports. For its behavior on that occasion the regiment was cited by the British and its commander was decorated. Perhaps you were not aware that two companies of Engineers fought alongside the Marines in the Bois de Belleau. And, when the gray hordes of Hindenburg were reeling back from the Marne, a report from the Rainbow Division ended: “Our advance troops, the 117th Engineers, are pressing the enemy closely.” But the story that will live longest in the annals of the famous corps is that of the sergeant of the railway regiment at Cambrai, who, surrounded by the enemy, refused to surrender and defended himself with his only weapon, a crowbar. When they found him, hours later, the crowbar was still clutched in his dead hand. About him, with crushed skulls, lay seven Germans.
The innumerable new devices produced by the Great War, however, required for their operation great numbers of specially trained men, so that the Corps of Engineers, from an organization consisting solely of sapper troops, found itself called upon to do more and more work in almost every branch of engineering. To meet these demands men were accordingly trained as specialists and assigned to specialist regiments and battalions, so that, when the war ended, the Corps of Engineers consisted of camouflage, car-repair, crane-operator, dock-construction, dredging, electrical and mechanical, forestry, general-construction, highway, inland-waterway, light-railway construction, shop, and operation, locomotive-repair, military-mapping, mining, pontoon park and train, quarry, railway-transportation, road, sapper, search-light (including antiaircraft), sound-and-flash-ranging, standard-gauge railway-construction, operation, shop and maintenance-of-way, supply, surveying and printing, trades and storekeepers, transportation and water-supply troops, organized as needed into companies, battalions, or regiments.
Now it was realized, from the very beginning, that the success of our armies in France would depend upon transportation. And, thanks to the threats of Pancho Villa, we had at least the framework of a transportation organization, for when it became necessary to send troops to the Mexican border in 1916, the War Department had organized a transportation service of sorts and had placed Samuel M. Felton, president of the Chicago Great Western Railway, at the head of it. Thus it came about that upon our entrance into the Great War there devolved upon Mr. Felton and his staff the gigantic task of obtaining in the United States and shipping to Europe the enormous quantity of transportation equipment and supplies required for the use of our forces overseas. In order to ascertain just what was required in equipment and supplies, a commission, headed by Colonel William Barclay Parsons, president of the American Society of Civil Engineers, and Colonel (then Major) W. J. Wilgus, formerly vice-president of the New York Central system, was sent to Europe within less than thirty days after the declaration of war. Upon the completion of its preliminary survey of the situation the commission dispersed, leaving Colonel Wilgus as the sole nucleus of the American Transportation Service in France, with Captain L. A. Jenney, formerly chief draftsman of the New York Central, as his assistant. Sitting on soap-boxes in an office in the Boulevard Haussman in Paris, with packing-cases for desks, these two officers outlined the general policy with respect to military transportation for the A. E. F. which the conditions seemed to warrant, and which General Pershing later adopted, and drew up the first requisition for railway and port equipment, materials, and tools. Colonel Wilgus, himself a veteran railroad man, quickly realized the vastness of the problem which confronted us and the gravity of the situation resulting from the dilapidated condition of the French railways and the appalling shortage of French rolling-stock. He accordingly informed the War Department that the American Army must prepare to operate its own trains, made up of its own locomotives and cars, from the seaports to the front, over the French railways under trackage rights. I might add that the principle of trackage rights, so familiar in America, was entirely unknown in France, and at first the French railway officials did not know what Colonel Wilgus was talking about, for they found it difficult to understand how it was possible to operate two systems of transportation over the same tracks at the same time.
The story of how the Engineers, under the direction of Brigadier-General W. W. Atterbury, formerly vice-president of the Pennsylvania, Director-General of Transportation, with Colonel Wilgus as his deputy and Chief of Staff, built up in France a transportation system which was one of the marvels of the war, is outside the province of this narrative, while the story of the production of railway material in America and its shipment overseas would require, for its proper telling, a chapter to itself. It is enough to say that, when the Armistice was signed, 60,000 men were engaged on railroad work of various kinds in France; more than a thousand miles of standard-gauge railway (equal to the distance by the Pennsylvania from New York to Chicago) had been laid; upward of 1,300 locomotives (300 more than are owned by the Atchison system) had been shipped overseas, and, had the war continued, we would have had in France by July, 1919, enough American cars to make up a train the caboose of which would have been leaving Paris when the engine was entering Berlin.
The Transportation Department had in operation between Tours, which was the headquarters of the Services of Supply, and Chaumont, which was the Great Headquarters, an all-American train, drawn by an American locomotive, driven by an American engineer, and, as a final touch, with its sleeping-cars in charge of former Pullman porters, in khaki, it is true, but retaining their grins and their whisk-brushes. Every one in the A. E. F. was inordinately proud of that train, which stood as a sort of visible proof of American accomplishment in France. It had been officially christened the “Atterbury Special” in honor of the Director-General of Transportation, but the soldiers had disrespectfully dubbed it the “Attaboy Special.” One morning, as a group of American congressmen, on their way up to the front, were standing on the platform of the Tours station, the special came roaring in.
“There’s an example of American energy and promptness for you!” exclaimed one of the politicians proudly. “What a contrast to those wretched French trains! Not an hour or so late, as they are, but on time to the very minute.”
“Pardon me, sir,” said a military policeman who had overheard the conversation, “that is yesterday’s train.”
When it was first proposed by the Transportation Department that locomotives should be shipped to Europe without being knocked down, the Ship-Building Board vigorously protested. There were no ships in existence, the board said, which could stand up under such an immense concentrated load. But the Engineers proved that they knew more about the strength of ships than did the ship-builders, and the locomotives—533 in all—were run out onto the wharves on their own wheels, picked up as easily as though they were baby-carriages by the giant gantry cranes, deposited in the hold—35 to a ship—together with their tenders, packed in baled hay, and upon arrival at the French ports were lifted out by the same method, lowered gently onto the rails, and a few hours later rolled off for the front under their own steam. The success with which the Engineers utilized business methods and revised specifications to meet American manufacturing conditions is strikingly illustrated by the fact that the cost of these locomotives, for which the French had been paying $51,000 each, was brought down to $37,000, thus saving to the American taxpayer some seven millions of dollars—a very tidy sum.
And, apropos of rolling-stock, here is a bit of secret history hitherto unpublished. When Villa’s raiders were threatening to destroy the railway-lines paralleling the Mexican border, the Engineer Corps designed and built a number of self-propelling armored railway-cars armed with 3-inch rifles, machine-guns, and search-lights. When the German submarines began their piratical operations along the Atlantic seaboard in the spring of 1918, these moving fortresses were secretly rushed up from the Rio Grande in order to afford protection to the undefended Jersey coast towns. It was well for the U-boat commanders that they did not attempt to shell Long Branch and Atlantic City as they shelled Scarborough and Broadstairs. If they had, the Engineers and their armored cars would have given them the surprise of their lives.
The non-military person does not ordinarily associate with war such prosaic occupations as lumbering, quarrying, and highway building. They seem, at least at first thought, to be in character essentially industrial. But it must be remembered that the workman played fully as great a part as the soldier in winning the Great War. In fact, the combat troops could not have held the line for a day had it not been for the labor battalions, which, without incentive or excitement, glory or reward, and in most cases without public appreciation, toiled so faithfully and unceasingly to build the wharves, to unload the ships, to lay the railways, to construct the roads, and to hurry forward, in an unending stream, the food for the men and the food for the guns. It is quite understandable, once you stop to think about it, that in order to maintain our great armies in the field, there were required immense quantities of lumber for building wharves, barracks, storehouses, hangars, and hospitals, and enormous amounts of stone, crushed rock, and gravel for metalling the roads, ballasting the railways, buttressing the bridges, and making concrete for the fortifications. When we entered the war the supply of lumber was not nearly equal to the demands of the Allied Armies, to say nothing of our own. And, though there was, of course, plenty of rock and gravel in this country, we could not spare the tonnage to ship it overseas, even had such a course been practicable. (Perhaps it has never occurred to you how vitally important an item gravel is in military operations. Yet at one time the Germans threatened the Dutch with war if the latter persisted in their refusal to permit German gravel to be shipped across Holland for the construction of concrete fortifications in Belgium.) In view of these conditions, it devolved upon the Engineers to organize and equip special forestry, quarry, and highway regiments, as well as numerous labor battalions, and hurry them overseas with orders to obtain the urgently needed materials from the forests and quarries of France.
Though Engineer officers of the regular establishment were, of course, given command of these specialist regiments, the other officers as well as the soldiers themselves were recruited from men trained in the particular sort of work which each regiment was expected to perform. How to obtain officers of sufficient experience in these various lines of industry, and in sufficient numbers, promised at first to be a serious problem, but it was quickly solved by the Personnel Division of the Engineers, which had had on file, ever since the war-clouds first appeared on America’s horizon, tens of thousands of letters from men trained in every branch of the engineering profession, offering their services to the government in case of war. Hence, when it was decided to raise a forestry regiment, it was a simple matter to turn to the files and find the names of thousands of men—mill-owners, forest-rangers, lumbermen—with their experience and qualifications carefully listed, who were intimately familiar with every phase of the industry, from tree to finished board. The best qualified of these applicants were offered commissions by telegraph and instructed to go out into the lumber country and recruit their companies and battalions from men who had worked under them or whom they knew. Soon the walls of every employment-office, bunk-house, and cook-shack from the pine woods of Maine to the spruce forests of Washington blossomed with posters calling for axemen, sawyers, log-drivers, timber-cruisers, mill-operators, cookees, teamsters, for immediate service overseas. The response was prompt and startling. From their camps on the Kennebec and the Androscoggin, from the Adirondacks, from the pine-clad shores of Superior and Huron, from the Michigan Peninsula and the North Woods of Minnesota, from the forested slopes of the Wind River, the Bitter Roots, and the Cascades, from the big timber of the Far Nor’west the lumbermen came pouring in, in mackinaws and parkas, in moccasins and shoepacks, in knitted toques and caps of fur, their scanty belongings wrapped in the blanket-rolls slung across their backs and often with their axes on their shoulders. Sinewy-limbed, saddle-colored, horny-handed, tough as the timber of the forests whence they came, these were the real pioneers, the conquerors of the wilderness, the last of the frontiersmen, and Europe will, in all likelihood, never see their picturesque like again.
The first of the forestry regiments, the 10th Engineers, sailed for Europe five months after the declaration of war, followed at short intervals by several similar organizations. Immediately upon their arrival in France lumbering operations were begun in the Vosges and the Pyrenees (so do not be surprised if the next time you go shooting in Maine or fishing in Michigan your guide interlards his conversation with French or Spanish phrases), using French mills at first but later installing plants of the American type. The enlisted men of the forestry outfits were, as I have said, for the most part lumbermen by trade, officered by men familiar with lumbering in all its details. The result was a striking illustration of what American energy and American methods can do, for the official reports show that mills which, under French management, were yielding 500 board feet a day, were made to yield ten times that quantity when operated by Yankee lumbermen. In the Vosges this work was carried on so close to the front that the plants were repeatedly bombed by enemy aircraft and shelled by enemy artillery, the forestry troops, though listed as non-combatants, frequently suffering heavy casualties. It took a high order of courage for these men to go unconcernedly about their business of tree-felling, hauling, and sawing with German shells yowling through the branches and bursting all about them. The sawmills were of the portable type, however, and when the fire of the German guns became too accurate and heavy, the whole plant was packed up and shifted to a new location. I don’t believe in letting loose upon my defenseless readers swarms of figures, but it will serve to give those of them who are familiar with lumbering some idea of what our forestry regiments accomplished when I mention that during the month of October, 1918, alone, they produced 50,000,000 board feet of sawed lumber, 80,000 cords of firewood, and enough standard-gauge ties to build a single-track railway from the Great Lakes to the Gulf.
In raising the quarry, highway, and inland waterway regiments, the same method was adopted as in the organization of the forestry battalions. Enormous quantities of crushed rock were required for concrete and for the construction and repair of roads, but though numerous quarries were available in the American areas, experienced quarrymen and quarrying equipment were lacking. Accordingly a special quarry regiment, the 28th Engineers, was organized in the United States in November, 1917, with a strength of 60 officers and some 1,500 men. A skeleton organization was formed by transferring a few officers and a small detachment of men from a road regiment, the new unit being raised to strength by giving commissions to quarry managers and superintendents and filling up the ranks with drafted quarrymen.
Spreading over almost the whole of France is a veritable network of navigable rivers and canals, of which the Engineers availed themselves to the utmost in the transportation of material and supplies. Transportation by the inland waterways was in charge of the 57th Engineers, this regiment being largely recruited from men who had had experience on the canals and rivers of the United States. In the days to come many are the tales that will be told by skippers of stern-wheelers on the Mississippi and captains on the Erie Canal of the days when they and their huskies of the Inland Waterways battalions moved the supplies for Pershing’s men up the Seine and through the canals of the Marne and the Rhône.
To the dredging, dock construction, and stevedore regiments was assigned the gigantic task of dredging the channels and harbors of the seaports which the French placed at our disposal, of building wharves and berths for the reception of American ships, and of the transferring of the cargoes from ship to shore. The magnitude of their task is shown by the fact that cargo shipments grew from 20,000 tons in July, 1917, to 1,000,000 tons in November of the following year, while the 23 ship-berths which the French Government originally assigned to us had nearly quadrupled when the Armistice was signed.
Unless you have marched with armies or trekked across hot and arid lands, you cannot know what it is to be thirsty—really thirsty, I mean; so thirsty that your tongue swells until it all but chokes you or lolls from your mouth like that of a panting dog. Water is infinitely more important to the success of a military operation than arms or ammunition; to a certain extent it is more important than food; for, though troops can fight for an amazingly long time on short rations, or even on no rations at all, they cannot fight without water. The vital importance of providing an adequate water-supply was learned by the French in Algeria and Morocco, by the British in India and the Sudan, where the deserts were strewn for miles with the bodies of soldiers who had died from thirst. In the Cuban campaign our armies had far more deaths from impure water than from Spanish bullets. During the Italian offensive on the Carso, that terrible plateau of sun-scorched rock which lies beyond the Isonzo, hundreds of men, Italians and Austrians alike, died from thirst, the Austrians being eventually compelled to retreat because the Italian artillery had destroyed the pipe-lines which supplied them with water. During the fighting on the Western Front during the last summer of the war, when the semitropic sun of eastern France beat down on the heavy-laden backs of the panting, sweating men, when millions of feet and hoofs ground the roads to powder and filled eyes, ears, throats, and nostrils with the yellow, choking dust, when the air reeked with the mingled stenches of leather, gasoline, sweating horse-flesh, and human perspiration, and when, as the canteens emptied, the men peered anxiously over their shoulders for the company water-carts, thousands realized as never before the truth of Kipling’s words:
Now, when a hundred thousand men and thirty-five thousand animals are crowded into a sector perhaps three miles wide and seven miles deep, the problem of keeping those men and animals supplied with water becomes tremendous. The responsibility for supplying with water the troops in the field fell upon the Army Water-Supply Service, which, as might be expected, was a branch of the Corps of Engineers. The Water-Supply Service was really a wholesaler of water, delivery being made at “water-points,” from which water was drawn directly by men and animals, the largest customers being, however, the ubiquitous two-wheel water-carts of the infantry and artillery. To supply these “water-points” every available source was utilized, springs developed, deep wells bored, village wells and cisterns cleaned out, streams purified and pumping-stations established, the aim being to provide water within a mile and a half of every consumer at the front. Ordinarily two gallons of water per man per day were furnished at the front, this quantity being sufficient for drinking, cooking, and lavatory purposes, but during the enormous troop concentrations incident to the St. Mihiel and Argonne offensives this quantity had to be materially reduced, during those periods of stress and action the men having scant opportunity for either cooking or bathing. It was impossible, however, to reduce the quantity for the animals, for each of which eight to ten gallons had to be provided daily.
Even under battle conditions the purity of the water was the first consideration, for impure water can work far more havoc with an army than enemy shell. In order to provide against this contingency, mobile laboratories for water-testing purposes moved in the van of the armies, and during the drives the Water-Supply troops were provided with poison-testing kits, for, warned by the experiences of the British in German Southwest Africa, where wells were systematically poisoned by the enemy, we took no chances. Sources of supply were, wherever possible, protected, it being considered almost as serious an offense for a soldier to contaminate a water-supply as for him to sleep on post. Where water was found to be polluted, the troops, no matter how thirsty, were under no circumstances permitted to use it until it had been filtered and sterilized. It is a curious fact that the chlorine used in gas-shell to kill Germans was used by the Water-Supply Service in minute quantities to kill an equally dangerous and far more insidious enemy—the microbic disease-carriers in the water. Special motor-trucks, equipped with pumping, filtering, sterilizing, and testing apparatus, time after time demonstrated that they were able to get into action and deliver pure water from a polluted supply within thirty minutes after their arrival.
In many cases the position of the troops and the nature of the terrain made it possible to deliver water only by hauling. This was done by means of trains of motorized water-tanks and by special tank-cars operating over the narrow-gauge railway systems, the tank trucks and cars being emptied into reservoirs built in strategic positions near the front. A common and quickly built reservoir consisted of a hole in the ground, a waterproof canvas lining, and a camouflaged cover. The lives of the tank-train truck-drivers were hard and exciting, for though the roads over which they had to pass in approaching the front were nearly always subjected to heavy shell-fire, there could be no let-up in supplying water for the troops on the firing-line. Most of the activities of the Water-Supply troops were between the locations of the light artillery and the heavy artillery, the men consequently working almost continuously within the areas under enemy bombardment. On one occasion, during the open warfare incident to the St. Mihiel offensive, the driver of a water-truck ventured so close to a German machine-gun nest that when he came back his tank was found to be better adapted for road-sprinkling than for water-transportation purposes.
It is scarcely necessary to remark that enormous quantities of material were required for the work of the Water-Supply Service, 60 miles of pipe and 300 gas-driven pumps being used during the St. Mihiel and Argonne-Meuse operations alone. As there were not enough Water-Supply troops—the 26th Engineers—for the needs of the army, it was found necessary to supplement their numbers with other Engineer units, motor-truck companies, and pioneer infantry, the Water-Supply Service of the First Army reaching a maximum of 3,500 officers and men.
One does not usually associate intelligence work with water-supply, yet the American Water-Supply Service had an intelligence section which was as efficient as that of any branch of the army. Information regarding the water-supply in the territory behind the enemy lines was gathered from all available sources, the Wasserversorgung maps captured from the Germans affording much valuable data, and the information thus obtained was published at frequent intervals, together with maps. The production of these water-maps finally became so highly developed that it was possible for the intelligence section of the Water-Supply Service to place full information at the disposal of the divisional intelligence officers within twenty-four hours after it had been received. So rapid was the American advance in certain sectors that scores of Boche pumping-plants were captured while still in operation, and turned to the task of supplying the thirsty Yanks. I might add that German prisoners, particularly of the corresponding enemy service, frequently were as successfully pumped for information as the wells sunk by the enemy were pumped for water.
One of the most picturesque and interesting developments of the war—and, because of the secrecy which surrounded it, one of the least known—is the work of the flash and sound ranging section of the Engineer Corps. For the benefit of the uninitiated—and most people are uninitiated, so far as this phase of warfare is concerned—I might explain that flash-ranging means the location of an enemy gun or battery by the detection of the flash, and sound-ranging by the location of the sound. Flash-reading, as it is called, is carried on by means of two or more observers provided with powerful telescopes, who are stationed at known distances apart. By “spotting” the flashes of an enemy battery and reporting them, together with the exact direction at which they occur, and by using these readings as a basis, a simple calculation in triangulation will give the location of the gun. So highly has this flash-ranging been developed that a gun can now be located within five yards, when the “core” of the flash can be seen. In principle the process is extremely simple, but in practice it is complicated by the fact that the observers may not train their telescopes on the same flash, in which case the gun position calculated at headquarters from their telephoned reports will be in error. This difficulty is met, however, by providing each observer with an outpost switch-set, by means of which he can flash a miniature light at the headquarters station at the instant he makes an observation, just as a light glows on a hotel telephone switchboard when a guest up-stairs rings for ice-water. When several of the observers flash their light simultaneously, it is assumed that they all probably caught the same flash, and their observations are then plotted. In other words, the line of sight of each observer is prolonged on a map until they intersect, the point of intersection corresponding with the location of the German gun.
Flash-ranging was also found to be of great value in checking the ranges of our own guns. If we were firing at a hidden target, a shell was timed so that it would burst when at the top of its trajectory. Observers would “spot” this burst, and if it was reported as being at the spot where calculations showed that it should occur, the gunners knew that they had the correct range.
Sound-ranging was carried on along much the same lines as flash-ranging, except that the readings were made by instruments instead of by observers. Large guns may be camouflaged so that their detection, either by aerial observation or by the flash of the gun when fired, is extremely difficult, but there is no known way to conceal the location of the gun from sound-ranging instruments, suitably placed and properly operated. This method became so highly developed that it was reported that during the latter months of the war over 80 per cent of the work of locating gun positions on the British Front was done by sound-ranging. The instruments used for this work are of a highly technical nature and for their successful operation require a skilled personnel. Recording instruments, so delicate that their use heretofore had not been dreamed of outside of experimental laboratories and then only in the hands of men carefully trained in their operation, were set up on the firing-line and operated successfully under battle conditions, even when the air was quivering from heavy bombardments and the earth was shaking from the deluge of steel. The sound-receivers, or detecting instruments, are located well to the front, whereas the recording instruments are several miles in the rear. A sound disturbance due to the firing of a gun somewhere behind the enemy lines is transmitted through several miles of wire to the recording instrument in the rear, and the sound records received almost simultaneously from several detecting instruments are traced on a sensitized ribbon, or tape of photographic paper, or on a ribbon of smoked paper, depending on the type of instrument used. The intervals of time elapsing between the arrival of the various sound disturbances is used as a basis for determining the origin of sound which produced the records. By this means over 100 new German gun positions were located in a single day on the British Front. In fact, before the assault on Messines Ridge the British sound-rangers had located practically every German battery, so that the British gunners had their exact range when the attack was launched. When the Armistice put an end to hostilities there were in operation along the American Front some twelve complete American sound-ranging sections, each covering a front of approximately five miles.
A sound-ranging section on an active sector of the American front usually consisted of four officers and from eighty to a hundred men, one-half of whom were specially trained in the care of instruments, observation work, and mathematical computations. On a stable sector the personnel of the section could, of course, be considerably reduced.
The principles, methods, and instruments employed by the sound-ranging section of the Engineers for locating active enemy batteries or for ranging the friendly artillery on any objective whose map-location was known were of an extremely technical nature and not easy of comprehension by a lay mind. So for the information of those readers who are technically inclined I have asked the Engineer officer who was in charge of sound-ranging in the A. E. F. to explain in the simplest possible language how the work was done. Here is his explanation. Make the most of it.
The principle employed by the sound-ranging section of the Engineers for locating active enemy batteries or for ranging the friendly artillery on any objective whose map co-ordinates are known is the following: The time of arrival of the sound from an enemy gun (or from the burst of the shells from the friendly artillery) at three surveyed stations inside the friendly lines determines the position of the source of the sound if simple corrections are applied for the temperature of the air and the direction and velocity of the wind. For example, if the three surveyed stations are on an arc of a circle and the sound of the enemy gun arrives at all three stations at the same time, then the gun must be at the centre of the circle. If the sound arrives first at the westernmost station and last at the easternmost, then the gun must lie to the westward of the centre. If the sound arrives earliest at the middle station and later at the flank stations, then the gun must lie between the centre of the circle and the stations. In practice six stations are used to insure greater accuracy, and graphical methods of computation are employed to shorten the time of calculation. Accuracies of fifty yards are regarded as average, and from one to two minutes for calculation are usually needed.
A somewhat different form of sound-ranging is used for the detection of aircraft at night. The apparatus for this aerial sound-ranging consists of large sound-gathering instruments which are used to direct search-lights in the location of approaching airplanes. When a bombing-plane approaches at night the hum of the motor can be heard at a distance of from one to three miles or more, depending upon the direction of the sound and the atmospheric conditions. The direction of sound, however, particularly when it originates in the sky, is illusive to the naked ear and search-lights were obliged to sweep the heavens in the general direction from which the airplane was believed to be approaching, in an endeavor to locate it. By the use of these detectors, however, the sound of an airplane can be detected at a considerably greater distance than by the naked ear, and, what is even more important, its direction can be determined within a very small angle—less than five degrees. In this way the area over which the search-light has to sweep is greatly reduced, and the chances of locating the aerial marauder are enormously increased.
Extensive experiments have been conducted in this country by the Engineer Corps in the development of these aerial sound-detectors. One form consists of four horns, two in a vertical and two in a horizontal plant, with listening-tubes leading from the small ends to the receivers of the observer’s head-set. These horns are mounted so as to permit rotation on a horizontal shaft and turning on a plane-table, the whole being supported on a sort of steel tower which, owing to its height and the fact that it cannot easily be moved, affords a rather conspicuous target for the enemy. The obvious disadvantage of this type is recompensed in a measure, however, by its accuracy and by the fact that it will so magnify a sound that the operators can hear the tick of a watch a hundred and fifty yards away. This apparatus is, however, large and cumbersome, and though excellent for seacoast and fortress defense, is not adapted for use in the field, where extreme mobility is required. For this latter purpose paraboloid sound-reflectors have been developed. These paraboloids are about nine feet in diameter, made in sectors of material similar to beaver board, and look like enormous editions of kettles used for boiling soap. They can be taken down and packed into small space for transportation, and are easily set up; being mounted on Ford chassis, they can go anywhere that a “flivver” can go. The paraboloids, like the horns, are directed by balancing the sound so that it is equally audible in both ears. These instruments have a sensitiveness double that of the unaided ear and by means of them a sound can be located to within three degrees.
When the officer in charge of one of these sound-detectors hears through the receivers of his head-set the rhythmic hum which denotes an approaching airplane—and I might mention, parenthetically, that experienced observers can tell with almost absolute certainty not only the nationality of the approaching machine but even the type and power of its engines—he orders several sound-readings to be taken at definite intervals of time. With these readings as a basis for the calculation, the probable location of the airplane at the end of the next time interval is plotted and the search-light is flashed in that direction just long enough to locate the machine. Quick work is required, however, for the airplane often travels at a hundred miles or more an hour and may abruptly change its course at any moment. Then, the plane once spotted, the beam of the search-light never leaves it, and the waiting crews of the antiaircraft guns get to work. Experiments are now being conducted to enable these listening devices to be used in synchronization with search-lights, so that, when the light is flashed, the airplane will be within the beam and no indication of the presence of the search-light will be given the aviator until he finds himself illuminated as a spot-light follows the movements of a dancer on a darkened stage.
In the autumn of 1917 the National Research Council, at the request of the Chief of Engineers, inaugurated an extensive series of search-light investigations, which, thanks to the enthusiastic co-operation of scientists, manufacturers, and certain government bureaus, resulted in a number of remarkable developments. Eighteen different kinds of search-lights were developed during these experiments, the first being placed in operation in France in October, 1918. This represented an entirely new form of light, more powerful than any heretofore produced by any nation. It weighs about one-eighth as much as the most powerful search-light theretofore produced, costs only about one-third as much, and has about one-quarter the cubage. Other improvements now in progress give assurance that its range will be doubled, its cost still further reduced, and its mobility greatly increased. And, what is of almost equal importance, the designs are now becoming so simplified that production need no longer be confined to highly specialized shops, but may be distributed over the country to all classes of machine manufacturers, thus making it possible to produce a large quantity in a relatively short time. With this new equipment the United States will possess a search-light having an effective range approximately twice that of the best search-light produced before the war, with four times as great a field. Two features of the latest types of lamps are particularly worthy of notice. These are, first, the “dish-pan” type of light, the chief characteristic of which is that it has no lens; and, second, the metal mirror, which is much more easily manufactured, is far less fragile, costs only a third as much, and possesses almost as great reflecting qualities as the glass ones.
The search-light used by the American forces for antiaircraft work is the heavy 60-inch seacoast type—the largest light known—lightened and modified for use in the field, with a range of practically 30,000 feet. As the result of recent experiments it has been found that the visibility at 12,000 feet was 85 per cent, while at 15,000 feet, or nearly 3 miles, it was 43 per cent. In order to obtain these standards of comparison for visibility for search-lights, an aviator was directed to fly back and forth through the beam a certain number of times. If the observers on the ground recorded the full number of passages across the beam, 100 per cent was registered, this occurring regularly at 5,000 feet, and in most cases during tests at 8,000 feet. The percentage of visibility was, in other words, the number of times the airplane was seen to the number of times it crossed the beam.
When warfare of movement becomes stabilized into position or trench warfare, it is almost certain that, sooner or later, one side or the other will resort to some form of underground attack. To permit of this subterranean warfare, certain conditions are requisite: the lines must be fairly close together, the level of the ground-water must be deep, and the ground itself must not be too hard. These obstacles to successful mining are not insuperable, however, for, preparatory to their assault on Messines Ridge, the British drove a tunnel which was a mile in length, and on the Carso I saw Italian engineers driving their galleries through solid rock. France and England early recognized the importance of this form of warfare and organized their miners accordingly, and, upon our entrance into the war, we too organized and sent to France a mining regiment—the 27th Engineers. It is estimated that by the summer of 1918 there were upward of 40,000 skilled miners on the Western Front, these soldiers of the pick and drill having been brought from the remotest corners of the earth—from the Yukon, the Rand, and the Congo, from Mexico, Australia, and California. In my “Vive la France!” I told, if I remember rightly, of the Cornish miners, known as “kickers,” who lay on their backs, as they do in the tin mines in Cornwall, where the galleries are so low that there is no room to swing a pick, and kicked away the earth by means of a sort of spur attached to their heels.
The officers of the American mining regiment were engineers who had had practical experience in all those far-off regions where men seek their fortunes in the earth. One of them, a young lieutenant, was diamond-mining in the Katanga district of the Congo when word reached him by native runner that the United States had decided to take a hand in the Great War. It took him four months of uninterrupted travel by horse, wagon, rail, and boat to reach the United States and offer his services to the Chief of Engineers. Another of our mining officers was a prisoner of the revolutionists in Mexico when the rumor penetrated to his prison cell that the United States had gone to war. That night he overpowered his guards, scaled the prison wall, made his way on foot across northern Mexico, the journey being relieved from monotony by several hairbreadth escapes from bandit bands, and reached the border in time to join the Engineers and go to France with one of the first contingents.
In former wars military mining was almost wholly confined to siege operations; that is, driving galleries under fortified positions and blowing them up. But the Great War developed an entirely new system of mining tactics, which included frontal and flank attacks, raids, enveloping movements, and other phases of war as fought on the surface of the earth. “Unlike the soldier who fights above ground,” explained a mining officer, “the miner has to be prepared for attacks not only against his front and flanks, but for assaults which may come from overhead or from underneath. In other words, he has four flanks to defend instead of two.”
A typical mining position, such as would be prepared on an active sector of the front, would consist of an upper level having a series of forked galleries, known as “feelers,” with geophone listening-posts at their extremities, and a deeper level, with numerous “fighting branches” projecting from it, to protect the lower flank. Just as the sentries in the trenches strained their eyes to detect any ominous figures in the darkness of No Man’s Land, so the mining sentinels, crouching over their geophones in the headings of dim-lit galleries, strained their ears to catch the faint sounds which gave warning that the enemy was approaching underground. The geophone, which has proved of incalculable value in mining warfare, is an instrument for augmenting small sounds coming through the ground. The American geophone, which is a highly sensitive, extremely simple, and easily portable instrument, is in no sense an electrical device, resembling, rather, the stethoscope used by physicians for testing the lungs. In mining operations two geophones are used, one for each ear, the instruments being so sensitive that the sounds caused by a fly walking on the wooden support of the geophone appear as loud as the tramp of a horse on the floor of a stable. If a sentinel on duty in an underground listening-post caught through his geophone a sound which was more distinct in, say, his right ear than in his left, he gently shifted one of the instruments, inch by inch, until the sound was the same in both ears. Then, by means of a compass, he took the magnetic bearing of a line perpendicular to that passing through the two geophones, which would give the direction from which the sound came. Meanwhile sentries in the other listening-posts were doing the same thing, so that, by the co-ordination of their reports and by triangulation, the enemy’s gallery could be located within a few yards.
If the mining officer was convinced that the enemy was driving a gallery for the purpose of putting a mine under his position, two courses of action would be open to him. He could remain on the defensive and check the enemy’s advance by the use of “camouflets,” this being the name applied to explosive charges which expend their force laterally, thus destroying the enemy’s gallery without causing a crater; or he could resort to strategy and engage the enemy’s attention at one point by exploding camouflets or by working noisily, and under cover of this diversion drive a fighting gallery toward his flank elsewhere. If, instead of being content to remain on the defensive, the officer in charge of mining operations decided to assume the offensive, he would engage the enemy’s attention at one point, either by exploding camouflets or by working noisily, and at the same time drive a fighting gallery toward his adversary’s flank. In this latter case the most profound silence had, of course, to be enforced in the fighting branch if the enemy’s geophones were not to give warning of its approach. No talking was permitted, the men wore felt-soled shoes and worked with trowels instead of picks, and the earth was carried out in cars with rubber tires. So silently were the operations in the fighting branches conducted that they would frequently break into the enemy galleries without the slightest warning, whereupon would ensue a struggle fought scores of feet beneath the surface of the earth, by combatants armed with picks, pistols, bombs, and knives, and illuminated only by flickering miners’ lamps—a battle so weird and strange in its character and setting that it seemed like the creation of a motion-picture writer’s brain.
One of the essentials for the success of a mining operation is the concealment of the spoil—i. e., the excavated earth—which, if piled in a heap at the entrance to the workings, would almost certainly be photographed by aerial observers, thus informing the enemy, as unmistakably as though it were announced on a placard, that a mining gallery was being driven. The French, in order to hide the spoil from their mining operations, conceived the ingenious plan of digging a shallow trench, usually only a few inches deep, and lining it with black paper, so that when photographed from an airplane it produced the effect of the black shadow cast by a trench of customary depth. They would then distribute the spoil from their subterranean galleries along the sides of this false trench, so that it appeared in the photograph to have been thrown up from it.
Dugouts have become such a commonplace in the past four years that few, save the miners themselves, gave much thought to or had more than the haziest ideas of the time, skill, and labor required in their construction. Take yourself, for example. You have read about dugouts and seen pictures of dugouts and have probably had relatives or friends living in dugouts. How long, then, think you, would it take a force of skilled miners to complete a front-line dugout large enough to accommodate a half-platoon? (For your information I might explain that such a dugout is 35 feet long, 9 feet wide, and 6 feet high, with 17 feet of overhead cover.) Using all the men that could be employed, and working from nightfall until dawn, it would require at least three months to complete such a dugout. If in the rear area, where the men could be worked continuously in shifts, it could be completed in about thirty days.