Underground Warfare 1914-1918

by Simon Jones

  The British artillery bombardment, although prolonged, was spread over too great a depth of front and the heavy shells were insufficient in quantity and reliability. The bombardment was inadequate in terms of sheer weight in destroying the German mined dugouts. The British also lacked skill and experience in using the barrage to keep the Germans trapped in their dugouts until the infantry had captured their trenches. Only on the southern Somme front did the attackers achieve success where the British 18th and 30th Divisions were assisted by French gunners and the French attacked south of the River Somme. Capitaine Thobie examined the dugouts captured in the French sector, which were of a variety of designs, ranging from a simple covered arch of corrugated iron to an elaborate complex built into the banks of the Somme Canal at Frize. The most common type was larger and deeper than those he had seen in 1915, 8m deep as opposed to 5–6m, and with multiple entrances. He described the difficulty of attacking ground beneath which extended networks of dugouts:

  With such buried shelters, potential embryonic forts, casemates and redoubts, one sees that it is very difficult to destroy the main enemy defence works. They are almost always so well concealed as to be impossible to detect. One is thus obliged to make an area bombardment over the whole zone where reports from prisoners or aviators might indicate their existence. And, in spite of the incredible expenditure of ammunition which the bombardment requires, one still finds many shelters intact and groups of men who overcame the bombardment because they had remained concealed. They are complexes, true octopuses, which surface suddenly from the ocean of iron and fire which every artillery preparation now comprises. They quickly extend their tentacles to the surrounding trenches and create in a few moments all the small pockets of resistance which our infantrymen run up against. If these miniature fortresses do not fall in the fury from the first attack they must then be encircled and progress is seriously impeded. We have enormous material means however: special shells, asphyxiating gases, etc… The tank appears to give invaluable help in these cases. …

  The German soldier is taught that in combat his survival depends on his tools. The capacity for labour of our enemy and his tenacity in the execution of any work increases considerably the magnitude of the achievement of our valiant troops. In Herbécourt, in Frize, in Combles, powerful deeply buried timbered dugouts, formidable redoubts, were taken even though the artillery was unable to destroy them all beforehand. Some of these shelters whose importance impresses us are already known; yet what an arduous task, what a jump in the unknown, when the time comes to leap over the parapet!13

  Periscope observation post installed underground. Dugouts were provided with periscopes and artillery observation posts were also installed underground. This example is German, but the French and British constructed identical positions. From Schwarte, Kriegstechnik der Gegenwart.

  The Allied response in 1916 to the German dugouts was threefold. Firstly they increased the quantity of heavy artillery to destroy them. Secondly, the coordination between the creeping barrage of field artillery and the advancing infantry was to prove more decisive than the ability physically to destroy them with a direct hit from a heavy shell. Thus the aim was to trap the Germans in their dugouts until the attackers were in their trenches, at the top of the steps. Thirdly, the problem of German troops emerging from tunnels after the attackers had passed over their positions was dealt with by troops which the British termed ‘Moppers Up’, assigned to clear out the deep dugouts with explosive, incendiary and gas grenades. These tactics were introduced during the Somme fighting of 1916, but were not fully developed until 1917. The German response during the Battle of the Somme was, partly, to go deeper. To protect against heavier guns they increased the thickness of earth from a recommended 6m to 7–8m and more in the case of command posts and medical or signals bunkers. Dugouts were required to have two entrances and be connected by tunnels to form accommodation for a platoon.14 This was to play into the Allies’ hands, as they developed the means to tackle the deep dugouts. In August 1916 the replacement of the German Chief of Staff, General von Falkenhayn, by General von Hindenburg and his principal assistant Lieutenant General Ludendorff saw the reduction in the reliance placed on deep-tunnelled defences. This change in command was to have major repercussions for German defensive policy in 1917, but did not prevent a series of defensive disasters for the Germans.

  The French and British regarded the trenches as jumping-off points for attacks rather than permanent homes for their infantry and this influenced their lack of use of deep dugouts in 1915 and 1916. In particular French defensive positions and accommodation in the front line were generally compared unfavourably with those of the Germans. However, despite a lack of manpower, following the increasing intensity of bombardments in 1915 they advocated the digging of deep shelters. From the end of 1915 they defined ‘bombproof ’ as withstanding systematic and regular fire from 150mm shells and also individual 210mm mortar rounds. Experience showed the French that shelters constructed by the ‘cut and cover’ method and protected only with logs and earth were unable to resist these heavy shells fitted with delay fuses and only mined galleries or dugouts could provide sufficient protection. They therefore required all shelters to be tunnelled, except where water was found too close to the surface to permit their excavation. The minimum head cover was 6m of hard, compact chalk: where this was not available a bursting layer of logs or concrete was to be included.15

  French design of deep gallery shelter with 6.7m head cover, as per instructions of January 1917. From an American translation, Notes on the Construction of Deep Gallery Shelters.

  French method of defence of a deep gallery shelter, showing loophole for rifle fire and mesh gates to hinder entry and catch grenades being thrown down the stairs. The stairs and ventilation holes of dugouts were increasingly provided with bomb-traps to contain the explosions of grenades. From Seesselberg, Der Stellungskrieg.

  The majority of British underground accommodation up to and during 1916 was of shallow cut and cover rather than deep tunnelled construction.16 Where the British took over trenches from the French on the Somme in the autumn of 1915 they found very deep dugouts cut into the chalk. However, anticipating the German change in policy a year later, the British regarded them as highly vulnerable where they were close to the Germans. Those seen by the commander of the Tyneside Scottish Brigade at La Boisselle were up to 30ft deep and held as many as fifty men:

  There were numerous deep dugouts in our front trench, but it would have been impossible for the men to get out of them in time to repel a surprise raid; in fact, these dugouts would have proved mere traps, so their use was prohibited, and the entrances were closed up by a network of barbed wire. The deep dugouts in the supports and reserve trenches were, however, found most useful not only for the shelter of the garrisons of the trenches, but for use as advanced dressing stations, company and Battalion Headquarters, and signallers’ dugouts, and for R.E. and ammunition dumps. (Brigadier General Trevor Ternan, commanding 102nd Infantry Brigade).17

  The Somme saw a major expansion of the use of such underground accommodation behind the front line to support attacks. For the assault on La Boisselle a significant portion of the Tyneside Irish Brigade was housed in a series of around forty-five dugouts in the reverse slopes of the Tara and Usna hills 1000yds (900m) behind the British front line either side of the Albert–Bapaume road. These were at about 20ft depth and linked by underground passages, although the labour available from miners in the Tyneside units made them the exception rather than the rule.18

  Following the Somme, the British used extensive dugouts for both headquarters and troop accommodation for the 1917 offensives at Vimy, Arras, Messines and Ypres.

  As the work of offensive mining declined, many tunnelling companies became wholly employed on this work in the run up to attacks. For the Messines operation they built twenty-four shell-proof battle headquarters for brigade staffs and twenty-eight battalion headquarters and dugout shelters for 200 office
rs and 10,000 men. For the Third Battle of Ypres the tunnellers constructed twenty-three brigade headquarters, sixty-two battalion headquarters, seven artillery, seven dressing stations, twenty-three observation posts and fourteen tunnelled dugout systems incorporating troop accommodation.19 Such a system beneath the ruins of the village of Wieltje, which housed the headquarters of the 107th Brigade in August 1917, was recalled by a staff officer, Captain Cyril Falls:

  Wieltje dug-outs! Who that saw it will forget that abominable mine, with its ‘town major,’ its thirteen entrances, the water that flowed down its main passages and poured down its walls, its electric light gleaming dully through steam-coated lamps, its sickly atmosphere, its smells, its huge population of men – and of rats? From behind sack-curtained doorways the coughing and groaning of men in uneasy slumber mingled with the click of typewriters. In the corridor one would fall over a runner, slimy from head to foot with mud, resting while he waited for a return message to the front line. One advantage only it had: it was safe within.20

  Communication tunnels were used immediately behind the front line to provide safe passage and many were dug in the Ypres Salient by both sides, although the wet sand made the construction of shallow inclined entrances difficult: in most places they were almost vertical. For the Messines operation these were constructed in four places to a total of 15,000ft length.21 Where the geology was more favourable in the chalk areas they were used even more extensively and the attack on Vimy Ridge on 9 April 1917 benefited more from such tunnels than from mines. The letter sent on 5 December by GHQ to Army commanders concerning the use of communication tunnels for the final attacks on the Somme was received as 1st and 3rd Armies were preparing for the Arras and Vimy Ridge attacks. Such tunnels were to be a major feature of the battles, but in many ways were quite different from the Russian saps used on the Somme. They were termed ‘subways’ and were not intended to extend far across no man’s land. Rather they were used to enable the infantry to get to their assembly trenches safely and secretly from the support trenches or from farther back. In particular the exposed Zouave Valley west of Vimy Ridge was identified as a vulnerable area as the Germans laid a barrage into the valley at the first suggestion of an attack. Six of the subways were tunnelled into the eastern slope of the valley, from 300 to 1,537yds. Mulqueen’s Company was responsible for four which, he recalled, were commenced before the arrival of the Canadians at Vimy Ridge. Blue Bull, Vincent, Cavalier and Tottenham Road were:

  ...named after the nearby communication trenches and a great deal of planning with the Division and Brigades preceded their construction. The 9th (Scottish) Division was in the line when Tottenham Road was started and it is probable that its location was fixed with an eye to its use if and when an attack were launched against the Ridge. Certainly before this and the other three tunnels were completed, their importance in the proposed attack became paramount.

  Two of the longest were dug by Mulqueen’s former Company, 172, on what was to become the 3rd Canadian Division front: the Goodman was 1,883yds and the Grange 1,343yds (of which part is open to the public in the Vimy Memorial Park). Twelve subways in all were used for the Canadian Corps attack, measuring in total six miles. They were constructed 6ft 6in in height and were wide enough for two laden men to pass. Most had electric lighting and some were equipped with tramways used especially for bringing forward ammunition for connected heavy mortar positions. The subways were also used to provide accommodation for battalion and brigade headquarters, cookhouses and latrines. They had their own water supply, piped from two large underground reservoirs each holding 50,000 gallons, and electrical power from generators. They also provided a secure conduit for signals cables and housed signals stations. The dressing stations in the subways were 34ft by 9ft and were dry and well-lit.

  Very careful attention was paid to traffic control in the light of the experiences on the Somme when the tunnels were so congested by wounded as to be unusable. The 4th Division scheme allocated military police to each subway with an officer at the eastern end and a sergeant at the western end and a telephone to keep them in communication. A plan of the subways was placed at each entrance and mid-way along, with direction boards at each junction. At the western entrance a large signboard guided troops coming across the Zouave Valley to the subway so that they could go directly to it. The officer had complete control over the tunnel traffic from nine hours before the attack. A system of traffic lights was used: when the assaulting troops were moving forward to the assembly positions only up traffic was permitted, the only exceptions being individual officers, medical personnel and runners. A red light at the tunnel entrance indicated that it was to be used for up traffic only and military police at each entrance enforced this. Thus the tunnel would be kept clear for the successive waves of the attack troops to get forward rapidly. Through one subway alone it was estimated that the traffic amounted to 9,700 men between 5 and 11 April.22

  The ends of some of the subways were used to create bored trenches using the Wombat borer. In five of the subways blown trenches were prepared using the borer, 6in diameter bores of about 200ft charged with ammonal cartridges. Three of these were actually blown at thirty seconds after zero, the longest being 195ft long and 14ft deep at the Chassery craters, where the 2nd Canadian Mounted Rifles assaulted, although it is unlikely that these blown trenches were used owing to the rapid success of the attack. The troops did not depart directly to attack from the subways, but the first waves used them to reach the assembly trenches about two hours before zero. The succeeding waves then used them where necessary. The capture of the ridge was a dramatic success for the Canadian Corps and the British Tunnelling Companies. An officer of 185 Company, whose unit had dug the Douai, Bentata and Zivy subways, wrote home enthusiastically to his father four days after the attack:

  Our work had been intimately connected with the early stages of the advance, and it is satisfactory to know from G.H.Q. that its purpose (the subways) was successful. We were attached to the Canadians and all the officers with whom we came in contact were enthusiastic about the results, and undoubtedly we were responsible for saving innumerable casualties in the initial stages and I dare say more will be heard of it later on.

  The twelve subways at Vimy dug for the 9 April 1917 attack. British subways are marked ‘S’, the German Schwaben and Volker tunnels marked ‘T’. From Military Operations, France and Belgium, 1917, Vol. 1.

  However, he later revised his view:

  It transpired a few months afterwards that except in a few cases the uses to which these subways were put were somewhat exaggerated, whilst the monetary cost was high. It is also noteworthy that the tunnels were not made for battle purposes of this kind again.23

  Like the Russian saps on the Somme, the subways were little used where the attack successfully secured the front line and where German mortar and artillery fire was prevented from interfering with the troops coming forward for the next phase of the attack.

  The tunnelling work planned for the Battle of Arras east of the town resembled more that of the later stages of the Somme offensive, with Russian saps driven across no man’s land with machine-gun positions or bored mines at the ends. The major difference was the opportunity to incorporate extensive existing underground spaces discovered in Arras and immediately behind the British lines and link these with the Russian saps. The British initially explored the Arras sewers. The sewers at Ypres had been used by the RE Signal Service as a protected means of running telephone cable where they were too small to admit a full-grown man, and a small Belgian boy was paid to take the line through. These sewers, however, were later destroyed by the German bombardment with 430mm howitzers.24 The Crinchon sewer in Arras by contrast was ‘a beautifully bricked tunnel’ 8ft high and 6ft wide, with footpaths on either side of the water course.25 It ran along the course of the old fortifications like a ring road on the eastern side of the old town and the British drove several inclined entrances from the cellars in the Grande Place and other locat
ions in the town to this sewer. Arras was built on hard chalk, and many of the seventeenth-century houses were provided with deep cellars, which were found useful for accommodating troops. Some 13,000 British troops were housed. In addition, in October 1916, the British discovered the first of a series of large disused underground chalk quarries on the eastern and south-eastern outskirts. The New Zealand Tunnelling Company was withdrawn from front line mining to exploit these for a future attack:

  Sketches of details of the Vimy the subways. From the War Diary of the Canadian Corps Chief Engineer.

  Caves and subways prepared for the Battle of Arras, April 1917. The British line before the German withdrawal is shown dotted and indicates the six subways extending into no man’s land, which were rendered redundant before the British attack. From Falls, Military Operations, France and Belgium, 1917, Vol. 1.

  These cellars and underground quarries formed the basis of the scheme on which the company now embarked. They were to be connected, opened up, and made habitable for troops, so that when the day for attack came the men could issue from them safe, warm and dry, and utterly unsuspected by the enemy. Two series of these caves and underground quarries were discovered stretching towards the enemy lines, one under the suburb of Ronville and one under St. Saveur and the Arras-Cambrai Road.