When you picture the battlefields of World War 1, you likely imagine muddy trenches stretching across no man‘s land, with soldiers huddled inside enduring artillery barrages and machine gun fire. But some of the most dramatic fighting in the Great War happened not above ground, but deep beneath it. Welcome to the dark, claustrophobic, and terrifying world of WW1 tunnel warfare.
Why Tunnel Warfare?
By late 1914, the Western Front had largely stagnated into a bloody stalemate, with both sides dug into elaborate trench systems that made frontal assaults almost impossible. Unable to advance overland, the Allies and Germans took the fight underground. The goal was to tunnel beneath the enemy‘s trenches, pack the tunnel with explosives, and blow them sky high, opening gaps for infantry to pour through.
As one British sapper put it: "We may not have been able to advance across no man‘s land, but at least we could advance under it."
Tactics and Techniques
Tunnel warfare required specialized skills and equipment. The British found their tunnelers in an unlikely place – coal mines. Hundreds of "clay-kickers" were recruited from mining communities to serve as military engineers, or sappers. Using timber to shore up the tunnel walls, they would lie on their backs, stabbing out chunks of clay with sharpened spades or bayonets.
The Germans largely relied on civilian engineers, but both sides raced to drive their tunnels under the enemy first. They also engaged in counter-tunneling, attempting to intercept and destroy each other‘s underground incursions. Tunnelers would press stethoscopes to the walls, listening intently for the scrape and chatter of the enemy. Poisonous gas, cave-ins, and violent underground clashes in the dark were constant threats.
Messines and the Somme
Perhaps the most dramatic episode in the tunnel war came at Messines Ridge in 1917. Over two years, British sappers had secretly dug over 8,000 meters of tunnels under the German-held ridge and packed them with nearly 1 million pounds of explosives. At 3:10 AM on June 7, they blew 19 massive mines in rapid succession, utterly destroying the German position in an eruption compared to a "miniature earthquake." 10,000 Germans were killed instantly and the blast was heard as far away as London.
Tunnel warfare also played a key role in the Battle of the Somme. Many of the distinctive craters still pockmarking the Somme battlefields today were made not by artillery but by underground mine explosions. Sites like the Lochnagar Crater, over 90 meters across, stand as vivid reminders of the incredible destructive power unleashed beneath the Somme.
A Buried Legacy
For the tunnelers of WW1, theirs was a largely unseen and unrecognized war within a war. Working in near-total darkness, in cold, cramped spaces with the constant threat of death, took a heavy psychological toll. Many suffered what would now be called PTSD. Their contributions were vital, but their experiences also uniquely traumatic.
Today, archaeologists are still uncovering the buried secrets of WW1 tunnel warfare. In 2011, French engineers using laser scans discovered a vast complex of British tunnels on the Western Front, remarkably preserved. And as recently as 2019, 270 German soldiers were found entombed in the Winterberg tunnel, sealed by a direct French artillery hit in 1917.
Projects to excavate these newly found sites are challenging, but they promise to shed new light on a largely subterranean theater of the Great War. By unearthing the tunnels, we are also unearthing the stories of the brave men who fought and died in them, finally bringing their hidden sacrifices to light.
