World War One is known for the advent of trench warfare, with opposing forces pitched against one another from dug-in positions. Yet as machine guns roared overhead at troops unable to advance over no man’s land, the only remaining way to undermine the enemy was by digging extensive tunnels beneath their trenches – and filling them with explosives.
Undermining the enemy
Between 1914 and 1918, the Allied British, French, New Zealand and Australian forces established a vast network of tunnels, particularly across the Ypres Salient in Belgium, as the Germans did so from the other side. The Germans employed tunnelling early on: in December 1914, tunnellers managed to lay mines beneath the Indian Sirhind Brigade and in the attack that ensued, the company was killed.
Yet the Allies quickly assembled their own special units of tunnellers guided by British Army Major Norton-Griffiths, an engineer on sewage tunnels in Manchester and Liverpool. In April 1915, 6 Allied-laid mines exploded, splitting open the German-occupied Hill 60.
Therefore, by the Battle of the Somme, tunnel warfare had become an inescapable characteristic of World War One.
The Battle of Messines
Shortly after 3.10 on the morning of 7 June 1917, British Prime Minister Lloyd-George awoke at 10 Downing Street to the deep rumbling sound of war from across the Channel. What the Prime Minister heard was the intense artillery bombardment the British launched against the Germans following a colossal explosion as 19 mines were detonated within 8,000 metres of tunnels underneath the Germans’ entrenched position.
The Battle of Messines continued until 14 June, and although initiated by the apocalyptic blast, the success of the British attack was the result of years of work. Since 1914, the Germans had been positioned on Messines Ridge that overlooked Ypres, giving them the advantage, so by 1915, recommendations to start extensive tunnelling below this tactical place had been made.
To break the stalemate, the British tunnellers crept underneath the German trenches and tunnel complex to lay the highly explosive ammonal, a combination of ammonium nitrate and aluminium powder. In fact, the Allies’ success was dependent on a second set of tunnels that had deceived the Germans: the true tunnels laced with explosives lay deep beneath, undetected. As the mines were detonated the German position was destroyed and thousands of German soldiers were instantly killed.
Field Marshal Herbert Plumer is commonly credited with masterminding the Allied attack, and the explosion was immediately followed by Plumer’s innovative tactic of the ‘creeping barrage’, where advancing infantrymen were supported by overhead artillery fire. Messines was indeed an extraordinary feat of planning and strategy that allowed the Allies to recapture the ridge and gain the first real advantage over the Germans at Ypres since the Battle of the Somme.
‘Clay-kickers’ and ‘sappers’
Plumer could not have facilitated one of the most successful battles of the war alone. Tunnelling was not an easy job and those digging faced long, dark hours underground let alone the possible horrors of being buried when tunnels collapsed or were exploded by enemy mines. For this reason, the task of tunnelling was not done by ordinary soldiers but miners and engineers.
Coal miners from Staffordshire, Northumberland, Yorkshire, Wales, as well as men who had worked on the London Underground and came from across the British Empire, were all recruited to dig. By summer 1916 the British had 33 companies of tunnellers at the Western Front. These tunnellers were used to the poor working conditions of mine-shafts and already had the strong team-work and discipline needed for military life.
The miners used a technique called ‘clay-kicking’ , in which one man with his back against a wooden frame would stab out chunks of clay (often using a bayonet) to be passed over his head and down the line of men along the tunnels. Clay-kicking earned the tunneller the name ‘clay-kickers’, although they were also known as ‘sappers’ meaning military engineers.
The technique was quiet and much quicker than the Germans, who continued to dig counter-tunnels in the hopes of destroying the Allied shafts. The British tunnellers would therefore leave someone below with a stethoscope pressed to the wall, listening to hear the Germans working and talking. When the German chatter stopped they were likely laying a mine, so the noisier they were the better.
Conditions worsened as the underground war progressed, with poisonous gas poured into the tunnels when British miners were discovered, accompanied by inevitable cave-ins. By the stalemates of the mid-war, the British army was in such need of tunnellers that the age and height restrictions were overlooked to find experienced sappers, who became greatly respected among the other soldiers.
The efforts of tunnellers during World War One left dramatic scars on the Belgian and French landscape. In the 1920s and 1930s, tourists would stop by the immense chasm of Lochnagar Crater south of La Boisselle, looking in awe at the capabilities of tunnel warfare, which by its underground nature has remained largely unseen and out of mind.
The immense depression at Lochnagar was created when one of 19 mines exploded on the first day of the Somme, 1 July 1916 and became part of an area so pockmarked by exploded mines that British troops referred to it as ‘The Glory Hole’.
Not only did tunnel warfare leave craters behind, but many of the tunnels and the stories of those who worked and lived within them remain buried. In early 2019, a tunnel complex was found 4 metres underground on the Chemin des Dames battlefront in France. The Winterberg tunnels had been struck by precise French artillery fire on 4 May, 1917, sealing the entrance – and exit – to the tunnels and trapping 270 German soldiers inside.
Questions remain over how to appropriately memorialise the site and human remains found there, which has led to a long delay in excavating the tunnels. Yet sites such as Winterberg pose exciting opportunities for archaeologists and historians alike to continue uncovering the history of tunnel warfare during World War One.