Military_(See_Mining

"Military (See Mining Io.714). - Until the invention of explosives military mining resembled ordinary mining, in that it consisted of driving galleries or tunnels under the enemy's defences, either with the object of penetrating to the interior of the place attacked, or of undermining the walls and causing them to collapse. The latter method was probably used by Joshua at the siege of Jericho, while he distracted the attention of the defenders by a military promenade round the walls.

When the miner was put in possession of gunpowder he used it first for blowing up the enemy's defences, and later for destroying his galleries and for making craters as points of departure for trenches. The term " mine " in military language thus came gradually to mean, not a system of underground galleries as in civil life, but a charge of explosive operated underground or under water.

The position of military mining in rgro is described in 10.716; contrary to expectation the first events of the World War seemed to indicate that mining was unnecessary, because the effect of the new heavy howitzers proved to be sufficient in themselves for the reduction of fortresses. But when the armies were settled down in opposing systems of trenches the heavy howitzers lost their preponderating role, and in the deadlock that followed oldfashioned methods reasserted themselves for trench warfare, such as grenades, trench mortars, and mining.

On the British front mining was started by the Germans. Before the end of 1914 there were two definite cases of mines under British trenches, and shallow mining systems were started in reply. It soon became evident that there was a probability of mining on an extensive scale, and that the existing R.E. units would be quite unable to supply the necessary personnel. It was proposed that coal-miners should be specially enlisted for the work, and their first detachment arrived in France in Feb. 1915. The formation of " tunnelling companies " followed, and during 1915 there was mine warfare all along the front.

In the early phases mining was chiefly a question of local efforts, partly defensive to counteract enemy mines, and partly directed against close objectives such as strong points in the enemy's trenches or a sniper's post. The mine systems were shallow, being rarely deeper than 20 feet. By June 1915 there was an enormous number of them, and the demands made upon the tunnellers could not be met. The need of a centralized control began to be apparent, not only to coordinate the local schemes, but in order that plans of larger scope might be developed in harmony with strategical ideas. Already in Aug. 1915 the first deep-mining system had been started, against Hill 60, with an object which was more than local; and questions of organization, of instruction, of intelligence and provision of stores all made direct touch with G.H.Q. essential.

Accordingly in Dec. 1915 a mining staff was appointed with an inspector of mines at G.H.Q., and a controller of mines at each army headquarters. The duties of the inspector of mines were defined as follows: (a) Preparation, under the instruction of the general staff, of mining schemes which were intended to have a bearing on the principal operations of the campaign, and examination of mining schemes prepared by the armies.

(b) Inspection, for the information of the commander-in-chief, of the progress of all mining work.

(c) Advising the engineer-in-chief on general questions affecting the personnel, organization and equipment of the tunnelling companies.

The officers of the tunnelling companies were chiefly mining engineers drawn from all parts of the world, many of whom had already had experience in the trenches. The men included, besides ordinary coal-miners, a number of specialists known as " clay kickers." These men worked on their backs with cutting tools fastened to their feet. Each man was strapped on a plank which was pushed forward as his excavation advanced, and in this manner, in good ground, he was able to work in a very small gallery and make rapid progress.

Since a good deal of unskilled work was required for removal of soil, transport of materials, etc., a number of infantry were attached to the tunnelling companies. Thus a tunnelling company on the higher establishment had 569 officers and men, and with attached infantry might be I,000 strong. By the end of June 1916 there were 25 imperial companies and seven overseas companies at work, with a total strength of about 2 5,000 of all ranks.

A new departure was the attachment of geologists to the mining staff; their advice was especially valuable in connexion with the water levels, which in chalk country varied as much as 30 ft. between summer and winter. In the German army the arrangements were much more elaborate, each army having a complete geological staff.

In addition to this it must be noted that for the first time in history the British army had immediate access to scientific brains at home, and could utilize at a moment's notice the most advanced manufacturing facilities of the country. The effect of this showed itself particularly in the development of listening apparatus. In former wars the human ear unaided had to listen for the sounds of the enemy working underground, and estimate his distance and direction; in this war specialists in England. were able to turn their attention to the production of listening apparatus as soon as the requirement was made known.

It naturally follows that the headquarters staff, with a very large and highly skilled personnel at their disposal, unlimited. resources, and the prospect of a long period of trench warfare, began to conceive operations far in advance of anything that had been contemplated in war.

Shallow mine systems had still to be continued to protect the British trenches, but at the same time deep galleries were started from 50 to 100 ft. below the surface directed against special objects. Naturally the two systems were sometimes worked together. The operations at The Bluff, between S t. Eloi and Hill 60, illustrate this. At this point there was a prolonged German offensive from Oct. 1915 to Sept. 1916. Working with a shallow system the Germans blew a large crater in Jan. 1916, which. caused many casualties and temporarily destroyed the British position. In July 1916 they blew four mines behind the British trenches, making a crater i 50 yd. by so yd. The British infantry had been warned by the mine officers; there were few casualties, and a barrage having been arranged for, the Germans could not secure the position. Just before this the British had started a deep gallery about ioo ft. below the surface. Working from this, and after some fighting in shallow systems, they blew four charges, totalling about 10,000 lb.

" Ten minutes before the blow two officers and eight men of a tunnelling company lay out in a shallow hole in a small crater which had been calculated as directly above the enemy workings. They started to dig down immediately after the blow, and broke through to the enemy gallery by midnight, which they found tamped with sandbags. These were all removed by 10 A.M. next morning, and about mid-day the galleries were entered by men wearing Proto apparatus - a complete survey was made, and 700 ft. of undestroyed enemy gallery, together with much apparatus, was found to have been captured. The enemy system was connected to our own shallow workings, and for the first time in its history The Bluff was reported as absolutely safe from underground attack.

" This final operation was a good example of a successful flank attack; our gallery was well below the enemy, and we succeeded in getting under him and along his front without being discovered." The Somme offensive in 1916 was an example of mining conceived and executed in connexion with an important attack, the plans being worked out in April, and a programme laid down. The underground work for this attack included mines for destruction of enemy works, galleries to provide advanced emplacements for machine-guns and Stokes' mortars, to be developed into communication galleries, and galleries for emplacements, ammunition, etc., only. There were nine mines containing altogether nearly 200,000 lb. of high explosive. They gave excellent results. The largest, having 40,600 lb. of ammonal, was placed at a depth of 75 ft. at the end of a gallery 300 yd. long; and it destroyed a salient covering ioo yd. of German line. The special point about the " galleries to provide advanced emplacements " was that a tunnelling officer was stationed at the end of each gallery, whose duty it was to break through the top of the emplacements for mortars and machine-guns, and also to break out at the end of the gallery to start the communication trench. Of the galleries for communication purposes only, 16 were connected up with the German lines. The methods of communication were three: by stepping up to the ground level and breaking out and digging; by placing a charge in a bore hole and blowing a crater in the enemy's trenches, then breaking out from the gallery into the crater, and thence into the German trenches; and by making a trench with a " pipe-pusher." Galleries for emplacements to ammunition depots were successfully broken through at the top, and the galleries were used at first for signal cables, runners and ammunition carriers; later for transport of wounded. This operation proved the value of these underground galleries in connexion with an attack.

In Sept. 1916, on the German side, large numbers of miners were sent home for industrial reasons, and mining activity was much reduced. The deep system controlled by G.H.Q., and directed against distant objects, was steadily pushed on, but the old shallow defensive systems were merely kept free of water and watched by listeners. The tunnellers thus set free were employed on what was practically a new development of mining, namely, construction of subways for infantry, and deep dug-outs.

By the end of Feb. 1917 nearly 20 m. of subways had been completed on the I., II. and III. Armies' fronts. In Sept. 1917 the Hohenzollern-Auchy subway system was completed, which made it possible to patrol 4 m. underground. At Nieuport subways and dug-outs were successfully made in spite of great difficulties with water and running sand. At the German attack a subway, not quite completed, east of the Yser, saved a considerable part of the infantry garrison.

The experience gained at the Somme was used to great advantage in preparing the attack of April 9 1917 on the Vimy ridge. In this case the mines, which were actually finished six months before the attack, were not of great importance, only two out of eight being used. The subways, which were made in three and a half months, were an interesting feature: - Twelve infantry subways from reserve line to assaulting trenches. These subways averaged half-a-mile long each, the shortest being 290 yd. and the longest 1,880 yd. They were 6 ft. 6 in. high and 3 ft. wide, with at least 20 ft. of head-cover, and were lit with electric light throughout, small lighting plants being installed in each subway. " The subways were supplied with dug-outs, assembly chambers, trench-mortar and bomb stores, trench-mortar emplacements, watertanks, dressing stations, signal offices, and in some cases brigade and battalion headquarters. They had numerous entrances and exits; the latter were broken out into advanced assaulting trenches on the last night, and the troops were able to file out into their assaulting positions through them. Maps on boards were hung at various points to show the position in relation to the surface. Tramways were laid in some of the subways, and these were found most useful for carrying up trench-mortar ammunition, stores and rations; signal cables were carried through the subways and signal stations were installed in them. The dressing stations, being dry and well lit, enabled the wounded to be easily attended to and kept in safety until they could be evacuated. Water-mains were also laid in some.

" Finally, the troops housed in the subways were able to rest in a safe, warm and dry place up to the time of the attack.

" The subways proved most successful, and, throughout, proof against bombardment, the only damage being done to some of the entrances. These were easily and quickly repaired by tunnelling company repair gangs, which were kept in each subway.

" The electric light in the subways was installed and run by the Australian electrical and mechanical mining and boring company. The lights were kept running throughout the whole operation without a breakdown. One plant actually ran 153 hours continuously. Ventilation was good, the only difficulty being in the case of gas attacks, when plenty of ventilation actually increased the danger. Specially appointed traffic officers (not tunnellers) were told off to each subway, and carefully trained beforehand in their duties." In this connexion the use made of the Arras caves is interesting. These were underground quarries of the 17th century, and were discovered by chance. They were utilized as shelters for men by connecting them with the front-line subways. The main galleries were 6 ft. 6 in. high and 4 ft. wide. The caves and galleries were lit electrically throughout, and water-mains laid. The caves accommodated about ii,000 men.

At Messines (June 7 1917) the main feature was the enormous scale of the explosions, unprecedented in military history. The total charges were nearly 1,000,000 pounds. There were 20 mines distributed over a length of about 8 m., the greatest concentration being 500,000 lb. on 4,500 yd. of front, from Hollandscheschuur to Ontario Farm. The largest mine was 95,600 lb. of ammonal, at a depth of 125 ft., at St. Eloi. The longest gallery was 720 yards.

The first idea of a deep offensive in the Messines-Wytschaete area was in the summer of 1915, when a deep gallery was started against Hill 60. Various deep galleries were started in 1916, but the final scheme had not begun to take shape until the summer. Many mines were laid months before the explosion. From June 1916 to May 1917 the Germans were searching for mine systems and blowing deep camouflets with heavy charges. Galleries were damaged or flooded in many cases, but by strenuous work most of them were restored in time for the attack. A very large amount of dug-out accommodation was provided.

The use of these enormous mines, whose destructive effects could not be definitely foretold, was naturally a matter of anxiety, but they were certainly successful. Ludendorff writes in his memoirs: " We should have succeeded in retaining the position but for the exceptionally powerful mines used by the British, which paved the way for their attack.. .

"All had been quiet and no sound of underground work on the part of the enemy could be heard at our listening posts. The mines must therefore have been in position long before.

" The moral effect of the explosions was simply staggering; at several points our troops fell back before the onslaught of the enemy's infantry." This was the last great operation with explosive mines. After this the tunnelling companies were largely employed upon dugouts and tunnelling. For instance, they made a number of subways through the canal bank near Boesinghe, for storage of material for bridging the canal. Subsequently they made approaches to the bridges by blowing gaps in the bank with bore holes. Other tunnellers were employed on roads and tramways. During the German offensive in 1918 the tunnellers were used for all sorts of purposes, including demolitions, and when the Allied advance began in August one of their most important duties was the removal of enemy land mines and booby traps.

## Advances in Technique

Probably the most important of these was in the development of " listening apparatus." In the fortress mining systems of ioo years ago an essential feature was the provision of listening galleries pushed out at regular intervals from the front lines of permanent defence galleries; but judgment of direction and distance of the enemy's workings depended entirely on the trained ear of the listener, which might easily be deceived. In the World War listening instruments were invented and employed for the first time.

After much experiment two types were approved, the geophone and the seismomicrophone.

The Geophone is on the principle of the stethoscope. A flat circular wooden frame contains mercury enclosed between two discs of mica. Two nipples on the edge of the frame provide for the attachment of ear-pieces with rubber tubes. Sound can be heard through the geophone about two and a half times as loudly as with the unassisted ear. A single geophone can do no more than magnify sound; for this purpose, however, it is very valuable, as it not only increases the distance at which enemy workings can be heard, but it helps the listener to distinguish between various sounds, such as picking, shovelling, talking, etc. With two geophones direction can be obtained, as follows: the two are placed at either end of a frame about 18 in. long, with a compass between them. To ascertain the direction horizontally the frame is placed on the ground and turned about until the sound is equally audible in both ears. The source of sound will then be in a direction at right angles to the line joining the two geophones, and can be plotted from the compass. If a bearing is then taken from another point, the intersection of the two will give the vertical line in which the source must be. To get the direction up or down, the geophones must be placed against the wall of the gallery. An example of the value of this method is given by Standish Ball: " A portion of our trenches had been captured by the enemy and heavily wired to repel our expected counter-attack. This was due to take place on the 27th of the month, and the miners were asked to assist in the enterprise and destroy the hostile wire. Owing to the short time available a shaft had to be sunk from the end of a sap, and the objective was reached on the 16th, just as the enemy were heard starting their mining operations. A geophone observation was immediately made, followed by further ones during the ensuing week. On the 24th the enemy were heard talking and laughing, without the aid of an instrument, only 6 ft. away, and to all intents and purposes on the point of breaking through. On examination of the previous observation, however, it was decided that the direction of his gallery was approximately the same as our own, and that he would probably pass along parallel to it. This is what actually happened, and the mine was blown successfully on the appointed day. If it had not been for careful and accurate listening the mine would have been blown prematurely and the success of the infantry attack jeopardized." The Seismomicrophone, an electric detector, does not give direction, but saves man-power. " As many as 50 galleries might be connected up to the switch-board of a central listening chamber, situated in some quiet position behind the mining system. In the event of sounds being heard from the detector in any particular gallery a listener was immediately dispatched with geophones to investigate." This economy of listeners was very important, especially as the end of a gallery is often a very dangerous place.

Average Chalk  
  
---  
  
Nature of sound

| 

Naked ear

| 

Seismomicrophone

| 

Geophone  
  
Picking. .

| 

125

| 

175 

| 

250  
  
Shovelling .

| 

70

| 

70

| 

120  
  
Talking

| 

12

| 

4; 

| 

50  
  
. Avera'e Clay  
  
Picking. .

| 

50

| 

70

| 

120  
  
Shovelling .

| 

8

| 

15

| 

30  
  
Talking

| 

5

| 

to

| 

15  
  
The following table gives (in feet) the distance at which sounds can be heard by the various methods in chalk and clay: - Mine Rescue Work. - One of the greatest dangers in mining has always been the presence in galleries of carbon-monoxide gas from the exploded mines. Owing to the quantity of mines blown and the large charges used this danger became very serious in 1915. " In six weeks one tunnelling company had 16 killed, 48 sent to hospital, and 86 minor cases treated at the shaft head and returned to the company billets." To meet this danger an instructor in the use of Proto apparatus was sent from England in June 1915, and schools for the teaching of rescue work were started.

The Proto apparatus consists roughly of twin cylinders of compressed oxygen, worn slung over the back, and supplying oxygen to a breathing bag containing caustic soda which absorbs CO 2 from the air exhaled. As this apparatus is in use in civil life it is not necessary to describe it here. The Proto set contains oxygen enough to last two hours. The Salvus apparatus is a lighter and more portable modification of the Proto, and is good for about half an hour. Oxygen resuscitating apparatus were also used. Apparatus special to the war were the mine stretcher, designed for dragging a man along a gallery and lifting him up a shaft, and a mine gas-testing set designed in the central laboratory at General Headquarters.

An officer of the R.A.M.C. having been attached to the staff of the engineer-in-chief for mine rescue work, the pathological aspect of the question was very thoroughly investigated.

Bored Mines. - These do not appear to have been much used in their original intention - that of pushing a thin pipe towards an enemy gallery, passing a small charge through it to blow a camouflet, and then filling the latter with a charge of 300 or 400 lb. of explosive. Larger bored mines with tubes up to 6 in. diameter were, however, used to some extent to make connexions. In some cases trenches were made in this way 14 ft. deep and 30 ft. wide. Trenches were also made by sinking bore holes from the surface and placing charges in them 4 ft. deep and 6 ft. apart. This method gave good cover in a very short time.

See The Work of the Royal Engineers in the European War 1914-19, section " Military Mining " (1921), which has been freely quoted in this article; also The Work of the Miner on the Western Front, 1915-18, by H. Standish Ball (Paper read at a meeting of the Inst. of Mining and Metallurgy, April io 1919). The mine warfare on the western front is discussed from the German point of view in Schwarte, Militarischze Lehren des Grossen Krieges (chap. ii.). (L. J.)