Underground Warfare 1914-1918

by Simon Jones

  Map of the German-held village of Carency. From Thobie, La Prise de Carency.

  Diagrammatic representation of the French demi-galerie and rameaux de combat. From Thobie, La Prise de Carency.

  An idealised French illustration of the use of the bored mine, which would only be possible in soft ground. From Thobie, La Prise de Carency.

  When the Germans blew (at G1), causing a crater but without damaging their workings, the French realised that they had reached further than they thought. They were also growing concerned about the condition of the unused mines at Beta and Gamma, and on 24 February mounted a raid in which they would be blown at 0430. At Beta the Germans were on their guard after the previous blow at Alpha, and had already been alerted by noise caused by the raiders assembling across the very narrow no man’s land. After the explosion, a French patrol was met promptly by German fire and the raid was abandoned. At Gamma the charge failed to detonate; the sappers remade the fuse but it still failed and, as there was not time to untamp the charge, this raid was also abandoned.

  The French could now hear noises underground at many places:

  The Germans show a tenacity which worries us and which can be countered only by determination and constant effort. There is not a moment to lose, no time for hesitation.1

  The Germans blew three mines in the first few days of March, but without seriously damaging the French tunnels, which they drove to meet them. On 6 March, 20/11 Company were reinforced by 14/5 Company, who took over the workings at Alpha (galleries 1-3). Working on the right-hand salients, where Gallery 7 reached 28.6m in length, the miners encountered a large block of sandstone which, being too large to move or cut, caused a detour. At 11pm the following night they met the timbers of a German gallery. The French miners removed the timbers and discovered a charged mine ready to fire. The Germans were apparently waiting for the French to advance further past the charge before blowing, when the unexpected change in direction caused them to discover the ambush tunnel. A sapper volunteered to enter the German gallery and cut the leads to prevent firing. The sapper then placed a charge against the tamping and discovered a second electrical primer which, when he withdrew it, detonated. The French dug the sapper free, but he was dead. They prepared a charge to destroy the German defensive galleries.

  On 12 March the Germans struck twice with heavy charges close to the French lines. The first destroyed three galleries, leaving them open to the sky and burying two miners, who were later rescued alive. The second destroyed the end of Gallery 5 from a point 40m from the entrance, burying five miners, part of a detachment of 80 miners from Lens attached to the 6th Territorial Regiment. The French could hear the buried men using a distress call distinctive to the Lens collieries. They charged Gallery 7 with 200kg of cheddite and dug to rescue the miners.

  This day is truly disastrous for the sappers. All our offensive galleries are destroyed completely or in major part and the enemy reaches close to our trenches. Will we have time to regain our balance and hit back? The infantry have a poor view of us and regard our sector as insecure. The garrison which is found close to the heads of our galleries is anxious and at every moment fears being lifted into the air amid a cascade of earth and chalk. At night the agitation grows. The pace of work is slow; listening becomes unreliable and it is necessary constantly to make allowance for imagination.

  We will pass through a very difficult period, and, it must be fully admitted, confidence begins to falter.

  On 13 March, the rescue operations at Gallery 5 continue with great difficulty. The calls of the miners are still distinguishable but the series of setbacks which we have just suffered leaves us in great distress and at every moment we wonder whether it isn’t our enemies who, to draw us into a trap, imitate the calls of the Lens miners…

  At 2 am, we find the flattened body of one of the buried soldiers; this discovery increases everyone’s dark forebodings. Work, despite everything, continues doggedly; the calls become increasingly distinct. Finally, after much effort and anguish, the four other miners surprised by the explosion are rescued. They are alive and safe but in a pretty poor state; they have spent twenty-five hours in the shattered gallery and, thanks to their coolness and courage, have assisted their rescue by clearing a three to four metre passage through the broken ground. (Lieutenant Hippolyte-Michel Thobie, 20/11 Engineers)2

  The French now believed that a large number of pioneers were pitted against them and later discovered that there were six German companies. As they staged a fight-back the mining took on an extraordinary intensity. After rescuing the men from Gallery 5 they charged it with 200kg cheddite and very quietly tamped it while the Germans worked vigorously, confident that their two heavy blows had destroyed the French defences. The French tamped very thoroughly, with 9m of backfill and five timber barriers, to minimise the damage from the explosion so that they could immediately resume their offensive. As the last listener left Gallery 5 before the blow he could hear the Germans still hard at work underground. After the blow the commotion and cries from the German front line raised the spirits of the French miners and gave them the feeling that they no longer needed to be pre-empted by the German mines or camouflets.

  In response to the two German blows, the French set out to strengthen their underground defences considerably by creating a two-level system with a transversal to form a subterranean front line. At Gamma they began branch galleries at right angles, which connected their tunnels 20-30m from their trenches to form transversals, which were to be a feature of a completely new tunnel system. They realised that they had to go deeper, with new galleries beginning from yet further behind their front line, from the second or even third line. If they remained in the systems started from the front line or just behind, they would be caught by deeper German tunnels passing beneath them. Shafts in the front line were vulnerable to German raids in which they might be destroyed or permanently captured, and with them access to the whole underground system. Two engineer companies, the 4/8 and the 9/2 Territorials (i.e. reservists) began work on nine new galleries, mainly at the two most threatened points, Alpha and Gamma. These galleries were started far behind the front line and passed under it at 15 to 20m depth.

  The new tunnels would all be linked by transversals once they were under no man’s land, forming an extremely powerful system. From the transversals they could listen at any point along the front and in the chalk could hear the Germans working 20m away. The galleries now had effective natural ventilation, doing away with the need for noisy hand-turned ventilators. The multiple entrances gave the miners greater confidence, as there was more than one means of escape should one entrance be blocked. They increased the size of charges and in mid-March exploded 400kg, while noting that the Germans continued to blow smaller charges and spent longer preparing them.

  Four French engineer companies plus attached infantry were now working on the operation, which they talked of as the ‘Siege of Carency’. Thobie emphasized the need for decision and confidence. The natural tendency for inaction to avoid criticism was largely compensated for by the energy of all those who took part in the siege. By 26 March they could hear the Germans underground on all sides, working constantly and loudly and blowing frequently, but to no effect:

  We are lodged deeply in the compact chalk in which the sound of the pick is transmitted a long way, there we can wait without fear. Work continues without danger, we are content to keep watch on the enemy who is not threatening for the moment. (Lieutenant Hippolyte-Michel Thobie, 20/11 Engineers)3

  There followed a curious calm that lasted almost a week. It was broken by a German charge blown near their lines which the French took to be a bluff. On the night of 16 April the French miners encountered the timbers of a damaged German gallery and entering found abandoned clothing, in the pockets of which were tobacco and an envelope dated 12 March. Canvas covering the walls was spattered with blood and they deduced that this was a gallery lost after their blows of either 29 March or 2 April. They believed that
they had panicked the Germans, but that they were pausing for breath and would hit back. This counter-offensive came on 22 April when the Germans blew and killed two French sappers. The French prepared and immediately blew charges of 100 and 400kg at 15m depth. In hard chalk neither charge broke surface.

  By early May 1915 the French miners had reached points close to the German trenches all along the line in front of Carency. When, on 5 May, an attack was finally ordered on the village for the following day, they were in a position to prepare a major assault with seventeen mines. However they had barely twenty-four hours’ notice to carry the explosives into the front line and charge, fuse and tamp seventeen mines, all the work to be carried out in one night, a total of 11.75 tonnes of explosives. To their relief the attack was postponed for 24 hours and all the mines, ranging from 200 to 1,500kg, were completed on time. They then learnt, however, that the attack was to be delayed again, for a further two days, to 9 May. This was a cause of anxiety: the French would have preferred to tamp on the night before the attack, in case of any problem with the firing leads. Moreover, a period of prolonged silence after intense activity would alert the Germans to the fact that they had charged and tamped, and might prompt them to fire their own mines to detonate those of the French. The French therefore resumed work in all galleries that were still open in an attempt to give the impression of normal activity.

  The infantry assault, part of the 2nd Battle of Artois, was at 1000 on 9 May and was preceded by a four-hour artillery bombardment that began at 0600. As at Éparges on 17 February, the blowing of the mines was part of the preparatory phase, during which the defences were breached in combination with the artillery. The seventeen mines were blown three and a quarter hours before zero during the bombardment.4 The mines were blown in batches by salient from 0645, so that blows did not damage adjacent mines, and the process took around twenty minutes. Thobie, in his highly detailed study of the battle, does not specify the time of blowing, which does not seem to have been regarded as critical. It may be surmised that the intensity of the bombardment already strongly indicated to the Germans the imminence of an attack and blowing the mines did not significantly rob it of surprise. Given the strong possibility of a failed circuit, the timing allowed the engineers to repair a broken lead and still blow during the preparatory bombardment:

  Suddenly the ground trembles, an enormous cascade of earth and chalk rises into space and falls with a terrible crash. A white and opaque cloud of smoke floods the trenches. It is the simultaneous detonation of the three mines of Epsilon salient. A few minutes later, another deep tremor, and this time in the shower which rises majestically is clearly seen a German; he will be found a few hours later twitching on the lips of the crater. From moment to moment, the ground is shaken by a powerful shudder which spreads into the distance with diminishing ripples. These are the seventeen charges, prepared by the 20/11 and 14/5 companies of engineers, which detonate in turn. Those of the 20/11, we have seen, are grouped in threes and contain together approximately two tonnes of cheddite. During the artillery preparation, a section was in charge of the firing which was carried out without a snag. For around twenty minutes, the entrails of the ground spout out demoralization, terror and death. And throughout, with method and precision, the hail of shells tears the air and beats down upon the enemy. (Lieutenant Hippolyte-Michel Thobie, 20/11 Engineers)5

  At Alpha salient the German front line and dugouts were either collapsed, partly buried by debris or completely obliterated along a line almost 300m in length. The defences were taken with little resistance; the mines, however, did not lead to the immediate capture of the village of Carency, which was itself converted into an extremely powerful fortress and only fell three days later. The mining attack was successful in the capture of the outlying defences of Carency and had benefitted from a German hesitancy which was not characteristic in other sectors. The French success, however, seemed to indicate the potential of mining in overcoming fortified positions.

  In response to the spread of mining Joffre’s Chief of Staff, General Belin, issued instructions on mine warfare tactics on 3 March 1915. These served to remind commanders of proper practice and attempted to establish principles for its use. They were wholly derived from pre-war practice, the scenario still being seen as one of siege warfare. Belin emphasized the parallels between underground tactics and those used above ground. He pointed out that mines were used most frequently to attack important parts of the enemy front, such as machine-gun or observation posts, armoured shelters, the exits of communication trenches or any centre of resistance. He advised commanders to use two parallel routes when attacking, 15 to 20m apart, in view of the uncertainty of success that one gallery had, and to use branch galleries from which listeners could protect the flanks. Work was to be pushed as actively as possible to anticipate the work of the enemy in developing countermines. The presence of a tunnel should not be revealed by exploding a charge prematurely and one should seek the most direct attack on the point to be destroyed. If one was attacked by mining, one should adopt either active or passive defence. The active defence required pushing galleries to meet the enemy until the moment had arrived to charge and profitably fire. In the passive defence, one would stop work, load charges and fire when the enemy arrived in range. Usually it was beneficial to advance and vigorously attack the flank of enemy galleries. Belin laid down technical rules: generally mines should be a demi-galerie, i.e. 1.30 to 1.50m high by 1m wide, to allow monitoring and good ventilation. If the length exceeded 40m then the rameau, 0.80m by 0.65m, should be used. Depth was always to be sufficient to be out of reach of shells bursting on the surface. Shafts were to be used only to gain depth more easily through rocky ground (entrances were normally inclines). Spoil should be removed so that the enemy was not alerted to work, either by its presence or by the colour of the extracted material. Against enemy advances, miners should seek to go deeper and use camouflets, which when deeply placed could be large without causing surface craters, the ground being left clear for the attack. Significantly, Belin’s instructions did not anticipate that mining would be initiated where it might prove counterproductive. During 1915 this was to be the case in many areas.6

  At Bois Saint-Mard in the Oise sector, the Germans were able to gain an advantage, owing to the lack of experience of the commander of engineers, by blasting through hard limestone to reach the French front lines.7 However, the effort required for the gains was highly questionable. The German 9th Pioneers made use of an underground quarry immediately behind their trenches from which to begin mining. The limestone required drilling and blasting and the sound carried for long distances. In early January 1915 the French infantry reported noises and their commander stated that he believed the Germans were advancing a deep tunnel. For the previous month they had also seen the exhaust from an engine coming from the German trenches which, it was surmised, was powering a drill. The commander of the 19/1 Engineers, Captain Gourlat, began listening from a shallow tunnel on 16 January, but three days later his superior, Colonel Prange, the commander of engineers for the 37th Division, ordered this work to stop. Prange denied that mining was possible through the hard rock, a response dictated both by logic and the regulations in the pre-war manuals of military mining. That evening the infantry commander reported that he had been perplexed by two explosions underground, which appeared to come from close to his trenches. When Gourlat listened, however, he heard nothing and concluded that the report was exaggerated. On 20 January Prange dismissed the reports of German mining and maintained that the noises were the sound of work in the underground quarries some distance away, transmitted through the rock. The same day, however, Gourlat heard the sounds for himself. They appeared to be getting closer and the Germans were firing field-gun salvos to mask the noise. On 25th Gourlat actually felt the blasting as vibrations coming through the ground. He then listened virtually continuously from midday until 8.30 the next morning and concluded that there were three German mining attacks, of which the
two closest were about 15m from the French front line. He detected a pattern of work from 3am to about 4am during which there was picking or drilling, followed by four or five explosions, which the Germans tried to mask by throwing grenades. He recorded explosions at about midday, 4pm, 8pm and midnight when they ceased, and they then resumed at about 8.30 the next morning and at midday. The Germans were clearly drilling boreholes and blasting and now seemed to be critically close to the French lines. Gourlat ordered drilling down to the hard rock with the intention of firing a large bored charge and inducing the Germans to blow a mine from their gallery before reaching the French lines. However, the drill head became wedged 2m down on account, he reported, of the clumsiness of the sappers, and work had to be resumed by hand with the pick. The noise of this picking, however, seems partly to have had the effect that Gourlat wished for, as that evening the Germans blew two mines, 4 to 5m in front of the French trenches. These formed craters 20 to 25m in diameter, wrecked 50m of trench and killed twenty-five of the trench garrison and wounded twenty-two.