Sketch of plan
The preceding sketch illustrates a plan adopted by the French which may be used in suitable soil for the offensive. This procedure often gives good results in deceiving the enemy. He thinks he is protecting himself. The defensive gallery starts from the front line and the offensive from the support. Both galleries are in the same vertical plane, the second being more advanced in the direction of the enemy. In the top galleries very little attempt is made to deaden the noise, while work below is carried on silently. An enemy listener easily confuses one with the other, and the offensive gallery passes under him. Distances D and D1are the same. The miner M confuses the two sounds, and the offensive gallery passes under him.
(Note: In many of the districts in France, where a sandy clay forms the top-soil and a hard chalk the subsoil, this method could only be adopted with difficulty, as the conditions are reversed. The top gallery being in clay, it would be comparatively easy to do noiseless work there, but extremely difficult to carry on the lower chalk gallery without noise.)
Referring to sketch C, direct attack may be made in this manner, or this method might be used as a feint, while the enemy is driven around behind the gallery at another point.
The usual measures of precaution employed in ordinary warfare above ground must be taken below ground whenever the distance of the enemy and the nature of the soil do not exclude all possibility of a mining attack.
It is essential to have: An efficient lookout and listening service (observation of enemy's work above ground, and listening-posts above and below); Means of defense underground—countermines.
The most reliable information will be obtained by underground listening with portable listening-instruments, such as the geophone, etc. Much confirmatory evidence is obtained by listening patrols at night in "No Man's Land" and by a careful survey of enemy trenches.
Several different arrangements can be adopted. The fan-shaped arrangement as shown in Fig. B, or the arrangement of independent parallel galleries (Fig. C). The second arrangement is preferable. The interval between galleries varies with range of listening in different soils. In clay, the distances between galleries should not be greater than 60 feet. In chalk this may be safely doubled. Listening-galleries are usually put out in Y-form, and these galleries are of smaller size, often 3 feet by 2 feet in cross-section. If desired, holes may be bored from the ends of these listening-galleries and geophones placed in them. Where time, material, and personnel permit, the mine-shaft is put in at the support-line instead of from the front line. This can only be done, however, when the situation allows of it. The galleries in Flanders seldom reach a greater depth than 25 feet to 30 feet, but in the districts farther south, in the chalk country, mining operations are conducted at any depth from 80 to 150 feet. A comprehensive German mine system was found in the Somme district at 200 feet. Naturally, it is a distinct advantage to get one's own defensive system in first and then sit tight and listen for enemy work.
The best defensive is often a strong offensive. A concrete instance of this is furnished by the experience of a British mining company who were ordered from Flanders to trenches in the chalk district at the Vimy Ridge to meet what was termed "an urgent situation" underground. The Germans were mining from chalk galleries at depths varying from 60 to 100 feet, and inflicting heavy casualties on the infantry occupying the British trenches by blowing large mines under their advanced positions. As a result the infantry were obliged to abandon many of these forward positions. The hard chalk subsoil of this district was covered with a sandy clay top-soil varying in thickness on this sector from 1 to 30 feet in depth. Some defensive galleries in the chalk had been started by the French miners when occupying these trenches. The British at once undertook the construction of numerous galleries in the clay top-soil. Their rate of progress was much faster in clay than that of their opponents in chalk, in addition to which they could proceed without noise. The programme was daring but entirely successful. The enemy continued to handicap their efforts at the outset by blowing often, but within some six weeks the British had succeeded in completely establishing their mastery underground. A few camouflets were blown by them in crossing "No Man's Land," but the majority of their mines were fired directly below the enemy's first line, and in some cases beyond. So intense was the fighting that on some occasions the British blew as many as four mines a night on a 500-yard front.
The question of the blowing and occupation of craters is usually determined in consultation with the infantry staff. Some occasions occur, as, for instance, when the enemy is met below ground, when it is necessary to fire charges which will form craters; but, as a rule, no craters are blown in "No Man's Land" until the infantry have been warned and plans made for their occupation or otherwise.
Camouflets are employed to a large extent to destroy enemy galleries when they are met below ground. The infantry officers occupying the trenches are always informed of an impending "blow" from the enemy, and dispositions are made to withdraw any troops occupying dangerous positions, such as outlying bombers' posts or automatic-rifle detachments, etc.
FIG. B, FIG. C
All ranks in the mining companies are warned not to create an alarm among the infantry occupying the trenches when enemy "blows" are anticipated. Mining officers, at their discretion, advise the infantry of the state of affairs when there is very active fighting underground and there is danger of casualties among the infantry from enemy "blows." Only in the latter event is it wise to inform them. Under ordinary circumstances, no information should be given. Considerable success in warning infantry of impending mines by the enemy has been reached by the British and French miners. They often estimate the time of enemy mines being blown to within a few hours. On the other hand, the enemy often prepare charges and hold them for long periods before firing.
It is most important to ascertain, by underground listening, the nature of the work done. Determination of the nature of the sounds in listening is of equal importance to their location.
The practice of blowing craters on every occasion in "No Man's Land" is discouraged, generally on account of the fact that it will prove an obstacle in the assault when the next infantry attack takes place.
Many craters are blown for tactical reasons, such as the obtaining of good observation-posts and, in other cases, to obtain enfilade fire from the rim of the craters blown. Previous to blowing these craters, plans will have been made with the infantry to consolidate them as soon as blown. The exact diameter of the crater will have been calculated and the position located in "No Man's Land," and a trench constructed, probably the previous night, which will intersect the rim of the proposed crater. As soon as the mine is blown, the infantry will consolidate their positions on the rims of the craters. Many craters are used to good advantage in the disposal of spoil from near-by mine-shafts. Considerable difficulty is found in obtaining new places in which to dump the spoil, especially on active mining sectors.
Many devices are employed to deceive the enemy when firing. Dummy picks are often suspended in the face of the gallery and operated regularly to imitate picking, etc. Other sounds indicating progress of ordinary work may be simulated in the gallery being charged, or perhaps rather noisy work going on in an adjacent tunnel. A little ingenuity here is advisable. Quite a large number of mines are fired at "stand-to" at dawn or dusk, average time, 4a.m.or 7p.m., depending on the time of year. Naturally, it is not wise to make these times regular. The "stand-to" times are common because of the fact that the enemy infantry also occupies his fire steps at these times. Care must be taken to withdraw troops occupying dangerous positions.
In the event of blowing a series of mines under the enemy trenches, plans are devised with the infantry in an endeavor to induce the enemy to occupy his threatened trenches in force. This may be effected by a "false" infantry attack, and other means.
The mine is an irresistible means of launching an attack. In a mined sector, the best troops completely lose their bearings for several seconds after an explosion. These several seconds prevent the machine-guns from firing, and the assailant gains a foothold in the first line, and often in the second. The extent of the underground operations in launching an attack naturally depends upon the size of the offensive, whether it be a battalion, brigade, division, or army offensive. The date has been set for the general attack. Mining units, in consultation with the staff of the forces employed, will elaborate their plans for the mining operations. (The battle of Messines furnished an excellent illustration of the value and use of extensive mining in launching an attack. In these operations, the British miners fired a large number of mines from galleries under the enemy front line, and in some cases below their supports. The charges in these mines varied from 15 to 50 tons each, and were all fired at "zero" hour, the minute at which the infantry goes over the top. Nine hundred and fifty thousand pounds of ammonal were used. Some mines had been charged for fourteen months and others for a year. One charge of 95,000 pounds formed a crater 125 feet deep with 186 feet diameter. The largest crater formed was from a charge of 70,000 pounds, depth of crater 86 feet, diameter 260 feet. These mines were in chalk and clay. The result was a complete demoralization of the enemy, and the first objectives were obtained with very few casualties.) The Germans deserted their lines for half a mile to the rear. These mines were fired on a front of several kilometres. The scheme of the offensive having been planned, galleries are driven under the enemy trenches and all charges laid ready for firing.
Throughout the brigade or unit attacking, all watches carried by officers are synchronized so that at "zero" time all mines are fired simultaneously. Frequently mining units are detailed to go over with the infantry in raids, or follow them over in attacks, for special demolition work, in which event they will usually carry portable charges of high explosives, and destroy enemy mine-shafts, dugouts, etc.
The use of mining to destroy the numerous enemy reinforced concrete shelters is now coming to the fore. Artillery-fire, even of the heaviest character, often fails to destroy these shelters, and engineers are called on to destroy them by tunnelling and firing with high explosives. In most cases, it is usually essential for the success of the work that a sufficient depth of clay is found, in order to proceed without noise. On some occasions they have been destroyed from tunnels in chalk, but this is increasingly difficult with the enemy's improved methods of listening. Smaller galleries must usually be driven. It often happens that very little cover to these galleries can be obtained and the work is more hazardous, but the success of these operations is undoubted if careful measures are adopted.
In June, 1917, the writer's company destroyed a German reinforced concrete machine-gun post by tunnelling from the Hindenburg line for a distance of 200 feet, through an average of 7 feet of clay above the chalk. For most of the distance, only 2 feet of cover was possible, but the operation was completed in a few days, and with a charge of 500 pounds of ammonal, placed right up against the concrete, succeeded in entirely destroying this German defense, and largely assisted the infantry in capturing another 500 yards of the enemy Hindenburg trench.
In the instance referred to, the enemy had a listening instrument set up in the chalk, but had evidently failed to hear the work in the clay above.
Nearly all the German trenches are undermined by a series of subterranean galleries, thirty feet or more in depth. As they retreat, in addition to building blocks or breastworks in the trench on top, they will also blow the tunnels underground. It sometimes happens, however, that these underground galleries are not destroyed behind them, and the enemy have taken advantage of this situation by waiting until the trenches are occupied in force by the pursuing troops, and then blowing big mines under them. Careful investigation of the enemy trenches occupied after an advance is essential, though this obvious precaution is sometimes overlooked. In all mining work of this character, speed and silence are of first importance.
No. 55.LINE CORPS SUMMARY OF INFORMATIONReceived up to 6 p.m., 17th August, 191—CONFIDENTIAL.This document is not to go beyond Battalion or Battery Commanders who are responsible that no copies risk falling into the enemy's hands.1.BRITISH OPERATIONS.1. (a) During last night and to-day on the11th Divisional frontthe 6th Lincolns Regiment and the 6th Border Regiment, by a series of enterprising patrols and bombing attacks, succeeded in occupying the whole of CONSTANCE TRENCH up to R. 33. a. 5. 4., near which touch was established with the 34th Brigade on their right, the whole of DANUBE TRENCH was also occupied and bombing posts pushed out to near JOSEPH'S TRENCH in R. 32. b.The enemy who had been holding these trenches fled in considerable confusion, leaving their rifles behind them.Point R. 32. c. 3. 9. was also occupied and direct communication opened with the 49th Division holding the LEIPZIG SPUR.(b) On the 49thDivisional front 2(diagonal) Lieut. Storm of the 5th York and Lancaster Regiment, who had been ordered to obtain an important identification, personally reconnoitred the enemy's trenches about R. 19. c. 8. 4. Returning he then led two platoons against the selected point and succeeded in forcing an entry. Considerable losses were inflicted on the enemy both by our surprise artillery barrage and during the bayonet and bomb fight which followed.The one prisoner necessary for identification purposes was duly brought away and the raiders returned with a loss of one man killed and a few wounded.(c) A German 5.9 Howitzer originally captured by the 48th Division near R. 32. c. 9. 1. and since covered by shell earth has been found again to-day.2. A hostile balloon (location unreported) was seen to fall in flames about 3 p.m.3.Artillery.25 direct hits on emplacements have been reported during the last 24 hours.At one position the pit was entirely blown away, 2 explosions occurred, and the dugout into which 2 Officers had been seen to run received 2 direct hits; several corpses were seen lying about.About 12 noon to-day one of our batteries caused a large explosion at R. 26. c. 3. 4. This was probably an ammunition store which has been reported by several prisoners to be located at this point.4.Prisoners.During the last 24 hours 9 prisoners have been captured by the II Corps, of which 7 were wounded.Total captured by II Corps up to 6 p.m. on 17th 26 Officers and 1,523 other ranks.Total captured by Reserve Army up to 6 p.m. yesterday 77 Officers, 4,478 other ranks (including 970 wounded).2.ENEMY'S OPERATIONS AND MOVEMENTS.1. Air reconnaissances carried out this morning report that a considerable train movement on the line from CAMBRAI to BAPAUME.No large movements of troops or transport were seen on the roads in the area opposite the Corps front.2. Much traffic on the IRLES-GREVILLERS Road, both ways, is again reported.3. SCHWABEN TRENCH is evidently occupied round about R. 33. a. 2. 7., men having been seen moving around there during the day.4. Yesterday the enemy blew up ammunition in evacuated gun pits to the Northeast of COURCELETTE, but it cannot be said there are definite signs at present of withdrawal from the line South of the ANCRE.5.Hostile Artillery Activity.Normal during the last 24 hours. LEIPZIG Salient, AVELUY, PIONEER ROAD in W. 16. b., the MESNIL area, WONDER WORK and THIEPVAL WOOD have been shelled during the day.Enemy's trench mortars have been quiet.3.ENEMY'S DISTRIBUTION, DISPOSITIONS and ORDER OF BATTLE.See Annexe.4.ENEMY'S DEFENCES.(a) Machine Guns.An emplacement, believed to be new, has appeared in BULGAR Trench about R. 26. a. 2. 4.Machine Guns have been located at:—R. 25. b. 7. 7.}Prisoners statementR. 19. c. 1. 5.}Q. 24. b. 1. 1.}R. 27. c. 3. 8.}(b)Dugouts Reported Occupied.R. 31. a. 53. 37.R. 32. a. 0. 9. to 2. 8.—holding 1 Company of the 77th R.I.R. (Prisoners statement).R. 27. d. 1/2. 3.(c)Headquarters Located.H.Q. of the 45th Res. Divn. is reported to be in HAPLINCOURT.H.Q. of the 212th Res. Regt. HAPLINCOURT.H.Q. of the 211th Res. Regt. LE BARQUE. Battle H.Q. of this Regt. is in dugouts about 200 yards behind WARLENCOURT.
No. 55.
LINE CORPS SUMMARY OF INFORMATION
Received up to 6 p.m., 17th August, 191—
CONFIDENTIAL.This document is not to go beyond Battalion or Battery Commanders who are responsible that no copies risk falling into the enemy's hands.
1.BRITISH OPERATIONS.
1. (a) During last night and to-day on the11th Divisional frontthe 6th Lincolns Regiment and the 6th Border Regiment, by a series of enterprising patrols and bombing attacks, succeeded in occupying the whole of CONSTANCE TRENCH up to R. 33. a. 5. 4., near which touch was established with the 34th Brigade on their right, the whole of DANUBE TRENCH was also occupied and bombing posts pushed out to near JOSEPH'S TRENCH in R. 32. b.
The enemy who had been holding these trenches fled in considerable confusion, leaving their rifles behind them.
Point R. 32. c. 3. 9. was also occupied and direct communication opened with the 49th Division holding the LEIPZIG SPUR.
(b) On the 49thDivisional front 2(diagonal) Lieut. Storm of the 5th York and Lancaster Regiment, who had been ordered to obtain an important identification, personally reconnoitred the enemy's trenches about R. 19. c. 8. 4. Returning he then led two platoons against the selected point and succeeded in forcing an entry. Considerable losses were inflicted on the enemy both by our surprise artillery barrage and during the bayonet and bomb fight which followed.
The one prisoner necessary for identification purposes was duly brought away and the raiders returned with a loss of one man killed and a few wounded.
(c) A German 5.9 Howitzer originally captured by the 48th Division near R. 32. c. 9. 1. and since covered by shell earth has been found again to-day.
2. A hostile balloon (location unreported) was seen to fall in flames about 3 p.m.
3.Artillery.
25 direct hits on emplacements have been reported during the last 24 hours.
At one position the pit was entirely blown away, 2 explosions occurred, and the dugout into which 2 Officers had been seen to run received 2 direct hits; several corpses were seen lying about.
About 12 noon to-day one of our batteries caused a large explosion at R. 26. c. 3. 4. This was probably an ammunition store which has been reported by several prisoners to be located at this point.
4.Prisoners.
During the last 24 hours 9 prisoners have been captured by the II Corps, of which 7 were wounded.
Total captured by II Corps up to 6 p.m. on 17th 26 Officers and 1,523 other ranks.
Total captured by Reserve Army up to 6 p.m. yesterday 77 Officers, 4,478 other ranks (including 970 wounded).
2.ENEMY'S OPERATIONS AND MOVEMENTS.
1. Air reconnaissances carried out this morning report that a considerable train movement on the line from CAMBRAI to BAPAUME.
No large movements of troops or transport were seen on the roads in the area opposite the Corps front.
2. Much traffic on the IRLES-GREVILLERS Road, both ways, is again reported.
3. SCHWABEN TRENCH is evidently occupied round about R. 33. a. 2. 7., men having been seen moving around there during the day.
4. Yesterday the enemy blew up ammunition in evacuated gun pits to the Northeast of COURCELETTE, but it cannot be said there are definite signs at present of withdrawal from the line South of the ANCRE.
5.Hostile Artillery Activity.
Normal during the last 24 hours. LEIPZIG Salient, AVELUY, PIONEER ROAD in W. 16. b., the MESNIL area, WONDER WORK and THIEPVAL WOOD have been shelled during the day.
Enemy's trench mortars have been quiet.
3.ENEMY'S DISTRIBUTION, DISPOSITIONS and ORDER OF BATTLE.
See Annexe.
4.ENEMY'S DEFENCES.
(a) Machine Guns.
An emplacement, believed to be new, has appeared in BULGAR Trench about R. 26. a. 2. 4.
Machine Guns have been located at:—
(b)Dugouts Reported Occupied.
R. 31. a. 53. 37.
R. 32. a. 0. 9. to 2. 8.—holding 1 Company of the 77th R.I.R. (Prisoners statement).
R. 27. d. 1/2. 3.
(c)Headquarters Located.
H.Q. of the 45th Res. Divn. is reported to be in HAPLINCOURT.
H.Q. of the 212th Res. Regt. HAPLINCOURT.
H.Q. of the 211th Res. Regt. LE BARQUE. Battle H.Q. of this Regt. is in dugouts about 200 yards behind WARLENCOURT.
ROUGH SKETCH ILLUSTRATING BREASTWORKS AND SYSTEMS OF UNDERGROUND GALLERIESROUGH SKETCH ILLUSTRATING BREASTWORKS AND SYSTEMS OF UNDERGROUND GALLERIES.Dotted lines represent galleries and tunnels from twenty to twenty-five feet underground.
ROUGH SKETCH ILLUSTRATING BREASTWORKS AND SYSTEMS OF UNDERGROUND GALLERIES.
Dotted lines represent galleries and tunnels from twenty to twenty-five feet underground.
Transcriber's Note:Minor typographical errors have been corrected without note.Irregularities and inconsistencies in the text have been retained as printed.
Transcriber's Note:
Minor typographical errors have been corrected without note.
Irregularities and inconsistencies in the text have been retained as printed.