Underground Warfare 1914-1918

by Simon Jones

  Our positions lie threateningly opposite the Cornillet hill, on which the Germans have built a well-known and dreaded position... The hill resembles a huge dragon stretched lazily out but ready at any time to be roused with a terrible anger, hurl fire, death and ruin on those who dare to come too close. The deep position appears unapproachable, impenetrable; protected and covered by the huge seams of chalk, one above the other, which form the hill. Inside life flows through three wide spacious main arteries with many galleries and entrances. By means of cleverly placed air shafts, fresh air gets into this underground world. And so it lay before us on 17th May; our commanders knew its strength, they were aware how dangerous and deadly these positions were for our attacking troops. The monster had to be slain at all costs.40

  The French bombardments had deforested the slopes, leaving the ground a white desert of chalk. They now rendered the shelters on the north slope, between the summit and the tunnel entrances, uninhabitable and identified the tunnel entrances from aerial photographs. The 476th Regiment was concerned that the tunnel was vulnerable to poison gas and altered the deployment so that the first and second battalions, minus a company, sheltered in the tunnel. The five remaining companies were in reserve in shelters. The tunnel housed the commanders of the 1st and 2nd Battalions, of which Major Wintterlin was senior, with headquarters, six companies of infantry (60 to 100 men in each), elements of two machine-gun companies, two platoons of regimental pioneers (80 men) and two platoons of the 376th Pioneer Company (80 men), plus artillery officers and medical personnel. On 17th the Germans repulsed some strong probing attacks. The French then turned an increasingly powerful fire on the tunnel and entrances, and the garrison expected an attack at any moment. Collapses and blockages to the ventilation shafts were cleared by the Pioneers on 17 and 18 May, but inside the tunnels were so airless that candles and cigarettes burned with a dim light. At daybreak on 18th the French bombardment reached its peak, with heavy calibre guns guided by low-flying aircraft with such accuracy that the central and eastern entrances were partly buried. After several hours work the pioneers managed to clear them and also used explosives to blow open the third entrance. The night of the 18–19 May was an ordeal with many casualties. As morning approached the French fire seemed to die down, but in the afternoon increased again to the strength of the day before. The German artillery was, however, still able to repulse the French infantry and they now prepared for an attack by using a much heavier destructive fire. To prevent repair to the damage they targeted the entrances with a large number of gas shells from midnight until 4.30am, which filled the tunnels with phosgene. The German gas masks proved adequate, however, and they managed to clear the tunnels of gas using ventilation units. The Pioneers erected partitions to try to keep the phosgene from penetrating into the whole system. That night the French barrage reached:

  …an extraordinary ferocity. Heaviest calibre weapons, gas shells and incendiary attacks raged on the hill and rear positions, until with the coming of the morning a slight drop was noticed. But the calm of this beautiful Sunday morning was short and deceptive.41

  On 20 May morale remained good in the tunnels: ‘with real comradeship officers and men together shared the dangers of the fighting.’ Early in the morning the French fire died down and most men were asleep in the tunnel. They had managed to maintain communication with the hill and regimental headquarters by runners and messenger dogs even under the most severe fire. After two hours lull, at about 7.30am heavy French fire began again and included 400mm shells, again directed extremely accurately by aircraft. One of the dogs was wounded and the other, arriving at the tunnel entrance with its report, searched confusedly for its handler, who had been buried under rubble. At 8am, Major Wintterlin sent word back that his food supply was still adequate but he urgently requested German aircraft to drive away the French spotter aeroplanes. The French appear to have been attempting to pitch heavy shells down the ventilation shafts.

  What occurred in the tunnel during 20 May can be partially pieced together from the accounts of those who managed to escape and a description of the aftermath by two French doctors. The entrances became blocked and the exploding shells produced carbon monoxide, against which the gas masks gave no protection. The Pioneers tried to seal parts of the tunnels to prevent the spread of the carbon monoxide, but ‘the gas crept through the seals and into all of the tunnels and had its sinister effect’,42 and parts of the tunnel fell silent as men succumbed and collapsed. At about 8.30am a shell came down a shaft near to the command post occupied by Wintterlin and the commander of the other battalion, Captain Count von Rambaldi, collapsing part of the tunnel. Wintterlin managed to escape but Rambaldi was buried beneath debris and desperate efforts began to free him. Wintterlin gathered his officers to discuss the situation near to one of the entrances when, about ten minutes afterwards, a second shell collapsed the tunnel at this point, killing and burying all fifteen officers. According to the chief medical officer, Dr Nagel, almost the whole destruction of the gallery occurred in a few minutes. The eastern tunnel, where the 1st Battalion was housed, was completely lost when both the entrance and the linking corridor collapsed:

  Those who were in the gallery succumbed in a few seconds to the carbon monoxide that the bursting shells at this point spread with great force. They underwent a gentle death, without pain, without suspecting that their sleep was to be for an eternity. Only one man, who was close to the ventilation shaft, was able to escape to the surface; when he shouted back down below there already reigned a deathly quiet and no reply came.43

  In the western tunnel the entrance was not destroyed but the situation was little better. Nagel found everyone rendered unconscious by carbon monoxide. His assistant medical officer Köbel found his way to the aid post but collapsed in Nagel’s arms. Another officer, Lieutenant Dauer, was seized with a terrible delirium. The large central gallery had remained intact and they moved into this area and erected screens to try to prevent the carbon monoxide from spreading. Those gassed who still showed signs of life were carried to the aid post and given oxygen. The hardest work was the attempt to rescue Captain Rambaldi, whose legs were trapped under a mass of chalk. After six hours of work he was freed and Nagel was astonished and relieved to see that his legs were not broken. Despite the efforts to isolate it, the carbon monoxide spread into the central gallery and by 2pm all the sleeping men had succumbed. Nagel had fifty oxygen breathing sets but they were inadequate for the men still in the tunnel:

  It was not a cheerful scene in the aid post, oxygen ran short, the gas victims suffered a great deal, groaned, coughed, were contorted in all directions, crawled on all fours to beg to be given oxygen to relieve them, it was terrible to be able to help only by administering morphine. Slowly a heavy tiredness started to invade me and I sought a corner to sleep. I could not lie on top of my dead comrades, not that, my conscience would not allow me. And so the comings and goings and the horror kept me awake and this saved me; those who fell asleep were lost.44

  At around 3pm Captain Süss, the senior surviving officer, sent back a report that the carbon monoxide was worsening and again requested cover against the spotter aircraft. An officer trying to reach the tunnel from regimental headquarters was wounded en route. By 4pm Captain Süss and Reserve-Lieutenant Killguss of the Pioneers were convinced that further occupation of the tunnels was futile and ordered their evacuation. Those infantry able to move were ordered into the shell holes and a trench running northwest from Cornillet. Only those engaged in rescue were to stay. The French gun fire on the entrances was so heavy that it prevented most from leaving. Nagel attempted to evacuate Rambaldi, but he declined to be carried through the bombardment and, despite urgings, he asked to be left in the tunnel. Nagel and the surviving medical personnel left the tunnel.

  The French launched their attack at 4.25pm and by 5.30pm had overrun almost all of the Cornillet position above ground, encountering some German resistance only in a small area west of Cornillet. The few German
s above ground in shell holes to the south of the summit were shattered by the violence and duration of the bombardment. They saw the attack launched and released yellow rockets to warn the observation posts and the tunnel garrison. However, the Germans were not able to launch a counterattack from the tunnel as before. An officer who was taken prisoner was astonished to see no one leaving the tunnel and shouted in vain down the ventilation shafts. He found the entrances either collapsed or blocked with bodies, with no signs of life from the garrison. At about 5pm Süss reported by messenger dog that all three entrances were blocked and his situation was critical. An order from regimental headquarters to evacuate the tunnel and word that a company was on its way never reached him, ‘…nothing more was heard or seen from Captain Süss and the rest of the men.’45 The French attackers swept over the tunnels, arriving at the entrances almost at the same time as the last shells of their barrage. They did not attempt to enter but threw in grenades and incendiary bombs and waited while the poison gas continued to take effect. During the night some of the garrison were able to escape via an airshaft and were immediately taken prisoner.

  Eventually two French doctors managed to enter the tunnels through the remains of one entrance, but inside they found no signs of life. After 30m they came across a heap of bodies, tangled one on top of the other. A little further on was a recess with a signal station, next to which were four bodies face down on the ground. Another was seated on a stool wearing a gas mask and still holding the telephone receiver in his hand. Some way on, where the main and transverse galleries crossed, the path was completely blocked by the fallen roof. The shell which came down the shaft and smashed the command post had sent carbon monoxide into the deepest corners of the tunnels. The corpses that they found in this passage had badly swollen faces with ruptured blood vessels from the explosion. From their appearance they did not appear to have suffered. The exit from the central gallery was completely blocked by a heap of bodies where men had tried to escape the tunnel and been torn apart at the entrance by French shells. There were perhaps one hundred men at this point, almost all young, lying in about five layers, wearing gas masks, some with fixed bayonets and carrying bags of grenades and filled water bottles. Others were still standing where they had suffocated. They noticed an officer lying on a stretcher, his legs in a plaster cast. A little further on were two machine guns, on one of which lay a German soldier, stretched out, his arms hanging lifeless. Ammunition and empty cartridge cases were scattered on the floor. In the tunnel commander’s dugout Wintterlin’s jacket, bearing his Iron Cross First Class, still hung on a hook. Large stocks of water, food and ammunition remained in the storage chambers. In the Aid Post wounded lay on the ground on mattresses and stretchers and alongside them the asphyxiated medical orderlies. Around a shaft and a large hand-operated ventilator a number of men were gathered who had tried to get fresh air but had succumbed to phosgene gas from the shelling around the shaft. At this point the French had to turn back because the air was still bad:

  One has to exit the tunnel as one entered, by climbing over the mountain of corpses, which reaches to the ceiling. Over the lifeless bodies, one comes out in the open at last, in the bright sunlight.46

  Some attempts to recover the bodies were made in 1933, but work was stopped by the danger of poison gas and the international situation. In 1973 workmen penetrated 12m into a tunnel and discovered human remains and during 1974–75 German Pioneers with French Army assistance recovered the bones of 321 soldiers.47 The German tragedy of the Cornillet tunnel demonstrated again the danger of reliance on underground defences once the attacker had developed tactics to deal with them and almost no soldier in the two battalions participated in the battle. The French demonstrated the ability to overcome such positions using highly accurate bombardment with gas and extremely heavy artillery and a very precisely timed barrage. The French captured the German Mort Homme tunnels on 20 August 1917 without their having been fully completed and again they formed a trap for the defenders. The French Moroccan Division took the ground above the Kronprinz Tunnel and guarded the entrances. The following day the garrison surrendered, comprising, it seems, 1,100 men, including a colonel and three battalion commanders.48

  The Cornillet disaster confirmed the need for the radical change in defensive tactics that the German Command was attempting to impose on commanders. After the British breakthrough at Arras, Ludendorff appointed Colonel von Lossberg as Chief of Staff to the German 6th Army to enforce the new methods, which contributed to the slowing of the British Arras offensive. The Cornillet Tunnel, however, was just one example of the vulnerability of tunnels and deep dugouts to these tactics.

  In June 1917 the General Staff issued a series of instructions based on the experience of the Allied spring offensives to emphasize again the new principles, which were not universally observed and which did not appear to be fully understood. Those issued on 10 June, based on the spring offensives rather than Messines, were emphatic about the danger of deep dugouts:

  Deep-mined dugouts in the front line and large tunnels have again proved to be mantraps. Any deep dugouts which may still exist in the foremost line should therefore be destroyed (at the beginning of the battle, at the latest), and large tunnels should be reduced in size by blowing up portions of them.49

  At the end of June instructions ‘The Construction of Defensive Positions’ were issued by German headquarters which were informed by the Messines battle.50 Again commanders were not fully following the new doctrine: instructions were more explicit and prescriptive. Dugouts in the old trenches, especially the first and also the second lines, had proved to be mantraps and strict limits were placed on the numbers of men accommodated in the forward zone. As the destructive fire of the enemy increased the mass of the infantry were to be moved from the forward trenches and dugouts and distributed in depth in the open before the enemy infantry attacked. During the battle continuous, linear trenches were no longer insisted on. Instead a pattern of shell holes was to be the basis of the defences, which would not be easily identifiable as defended positions and would be held by groups and single machine guns. The shell holes were to be linked by tunnels lined with mining frames and the spoil concealed by being thrown into nearby holes or scattered over the ground. The first line was to contain small dugouts for only one-sixth of the garrison. These were little more than shelters and prefabricated galvanized corrugated iron sheets were introduced for this purpose, known as Schützenhöhlen or Siegfried shelters. Deep dugouts were only to be constructed in the second and third lines. In the second line, these were to accommodate a third of the trench garrison and beyond that half of the garrison was to be in dugouts. Where it was possible to construct mined dugouts they were to be covered by 8–10m of earth. There were to be at least two exits, wide and high enough to allow rapid exiting by the garrison, supported by strong timbers and well protected. The use of old trench lines was warned against owing to the prevalence of dugouts in the front line: ‘The majority of the dugouts are in the first trench. This leads to crowding in the forward line with disastrous consequences.’51

  Where the defence line was in the back areas, the first trench was to be abandoned and a new one dug in front. In the Flanders the presence of ground water dictated whether dugouts could be constructed and the German defences depended especially on concrete bunkers, which were shellproof and could be rapidly evacuated to meet an attack. Instructions in October 1917 limited the size of dugouts to accommodate no more than two NCOs and sixteen men.52

  German defence of shell holes, showing the positioning of the entrance to avoid the fall of flat trajectory shells and anti-grenade mesh which could be rolled down to protect it. Although this accommodation might be in the area of the front line, the small dugout would house a few men only in line with German regulations. From Seesselberg, Der Stellungskrieg.

  The use of Siegfried shelters, a three-man shelter in a front line trench, designed to prevent men from being trapped by attackers in deep dugouts. Th
e prefabricated sections were also used to make secure dugout entrances. From Seesselberg, Der Stellungskrieg.

  These restrictions severely limited the comfort and protection afforded to soldiers in the front line and caused Ernst Jünger to look back in the middle of 1918 with nostalgia at his accommodation at Monchy two years before, but also to reflect on the dangers of the deep dugouts:

  Little can be said for the dugouts... They are what are called Siegfried dugouts, that is to say, semicircular holes, penetrating the wall of the trench to a distance of three metres and protected from above with a covering of earth, at the most two metres deep. The frame consists of thin circular sheets of corrugated iron that scarcely support the weight of the earth heaped on them and give only just room enough for two men to lie at length. … those who bivouac in them and who in their moments of rest keep their eyes fixed on the zinc roof, the mouse-trap that must infallibly crush them at the first direct hit. … Compared with earlier days, then, when we dug ourselves ten metres and more into the earth, there has been a serious decline in security. … The war has become more mobile and such works of construction no longer pay. And then it must be admitted that with the attack on Verdun the series of great onslaughts of material made the contrast between the safety of these gigantic strongholds and the front-line trenches, swept with flame and shattered with shell, far too great. But apart even from the moral factor, the occupants of these caverns, in the event of an attack, had as far to go before they could reach the trench as if they had to climb the stairs of a four-storeyed house. Thus it often happened that they had a warm reception half-way up from bombs and burning phosphorus without being able to strike a blow, particularly when the men on guard in the trench had long since given their lives in its defence without any one below being any the wiser.