Fighting the Boche Underground

by H. D. Trounce

In the same way as the general principles of tactics in open warfare agree with those of trench warfare, they are guided by the same logical reasoning. Many considerations must be studied before adopting any plan of offense.

With regard to depth below the surface, the miner must be guided by the elevation of his objective and by the nature of the strata through which he will have to work. In most operations the water-level is an important factor in considering depth.

It must be always borne in mind that mining is not an independent service, but is employed in connection with the other arms of the service.

Underground activity, either offensive or defensive, is first observed from those points in our lines nearest the enemy. All enemy trenches facing salients of our lines will be the object of particular attention and closest daily observation. This observation of the first-line and support-line trenches should disclose the presence of enemy underground works and their approximate location. For their definite location, the most careful listening underground must be done.

Aeroplane pictures are a source of much valuable information if studied very carefully. Aeroplane photographs covering several weeks, and if possible several months, are procured from the nearest squadron of the air service. The use of a strong magnifying glass will probably discover chalk mounds where fresh heaps are, by comparison with previous aeroplane photographs, shown to be growing in size; and other features or changes which will afford useful information on careful study. Particular attention is paid to new trenches in the enemy's lines. In fact, any change from week to week in these aeroplane photographs is carefully accounted for. If further pictures are desired, particularly just after craters have been blown by the enemy or ourselves, they are furnished by the air service. The enemy's lines are studied from day to day with field-glasses. Perhaps the accumulation of sand-bags different in color to the others will be noticed, or freshly placed earth, white and less dull in color than that of the parapets, which have been washed by the rain and blackened by explosives. As a matter of fact, in mining operations in Flanders, where blue clay was encountered, the bags containing the clay (different in color to surface clay) were so distributed along the front-line trenches or breastworks on both the enemy and British trenches that it was a matter of considerable difficulty to obtain much information from this source. It was, of course, common knowledge that both sides were engaged in mining and fairly accurate information as to position of enemy galleries was deduced, but the actual location of enemy mine-shafts was very difficult to determine, as quite a number of mine-shafts emanate from dugouts and are connected up with others.

Listening reports give a fair idea of where the enemy's galleries are, and plans are made up showing the suspected location of enemy galleries or mine system. These plans are developed in accordance with the evidence furnished. Careful observation may show that a number of men come up the communication-trenches regularly to certain spots and there disappear from view. One may notice carrying parties coming up with timber, by catching sight of the timber above the trench. Infantry listening patrols, who have been listening in "No Man's Land" at night may have heard the sound of machinery or ventilators at work, or some other sounds which go to prove the existence of enemy mining, or the location of mine-shafts, etc. It is important to listen in "No Man's Land" at night, in order to obtain definite information or confirm the reports from infantry.

Sufficient evidence being obtained as to probable location of enemy mine-shafts, or dugout entrances, etc., there is difficulty in having these places "strafed" by our own trench-mortars and artillery.

In the desire to obtain evidence of the enemy's activity underground, the proper camouflage of one's own spoil-heaps and entrances cannot be neglected.

It is essential to have a scheme of attack. Numerous attacks have failed on account of there being no clearly thought-out plan. A common mistake has been failure to anticipate possible counter-mining by the enemy, and to commence the attack without guarding against it.

Study of the objective and the ground will therefore furnish the information necessary to settle the essential elements of the scheme.