Meet The Tunnelers That Won WW1

Let's investigate how "human moles" won World War 1 with the biggest blast before Atomic Bombs in the Battle Of Messines!


On the 7th of June 1917, during the First World War, the village of Messines, Belgium, was rocked to its core by a massive earthquake or at least, that’s what the German soldiers occupying the area thought it was.

It was only when they saw the bodies of their comrades flung into the sky, which was burning orange with flames, that they suddenly realized this was no earthquake, this was a blast! One so huge it annihilated some 10,000 German soldiers, injured thousands more, and produced shockwaves felt as far away as France!

biggest blast before atomic bombs battle of messines explosion

But the most incredible part was that the explosion hadn’t come from a bomb or artillery that rained down from above, it had originated from right under their feet. How on earth had something capable of an explosion of this magnitude gone completely undetected by so many men?

The answer lies deep underground, where a specialist unit of Canadian, Australian, New Zealand and British tunnellers had worked tirelessly to set up one of the largest man-made explosions in all of human history. While the horrors of the trenches have been well documented, the story of these tunnellers isn’t as widely known, though it’s arguably even more harrowing and their history will blow you away!

Australian soldiers with a tunnelling machine in France during WW1

Tunnel Warfare During WW1

To uncover the full story, first we need to rewind to the start of World War One. In August 1914, German forces ripped through French and Belgian defenses. Their advance wouldn’t last, though. One month later, at the Battle of Aisne in eastern France, French and British forces stubbornly halted the German offensive.

With both sides struggling to overpower one another, a stalemate ensued. They each dug trenches some 7ft deep into the earth to hold their positions, while protecting troops from enemy artillery by sheltering them in lines of fortified dugouts. While the trenches provided both sides with an almost impenetrable defense, it also meant it was virtually impossible to launch an attack on the enemy.

Unsurprisingly, a deadlock followed. To try and break the stalemate, both French and German troops began mining. You may be thinking that the battlefield isn’t the best place to start looking for oil or diamonds! But they weren’t digging for underground treasures; they were after something far more valuable.

The aim was to tunnel under the strip of no man’s land between them, until they’d reached the underside of the enemy lines. Once there, they’d plant explosives and later detonate them, hoping to obliterate the opposition’s trench line.

blasting enemy line

In December 1914, the brutality and effectiveness of this tunnel warfare was seen for the first time, but not in the Allied Forces’ favor. At the Battle of Givenchy, ten German mines, each weighing 110 pounds, exploded under Allied lines.

The blasts, and the following infantry attack, resulted in the death of over 800 men and the entire British Indian Sirhind brigade was wiped out. Not only was the attack devastating to the men who lost their lives, but also to those who heard the horrifying tales.

Soldiers were accustomed to bullets firing at them, they could hear shells coming their way. But the prospect of an explosion from below was more concerning as they had no idea when and where it would come from next. A new method to winning the war was born, and it was terrifying.

detecting underground explosion in ww1

In response, you’d expect the Allies, specifically the British, would have stopped at nothing until they annihilated German positions with tons of explosives. However, they did zilch. British army generals claimed Britain didn’t have enough engineers on the front line to successfully carry out underground warfare.

Hellfire Jack and the Clay-Kickers

Entire regiments were getting wiped out, and Britain had no response. That was until John Norton-Griffiths stepped in. Otherwise known by the awesome nickname ‘Hellfire Jack’, he had a background in mining. When war was declared, his mining company, ‘Griffiths & Co’ were extending Manchester’s drainage and sewer systems. And it was then he had a eureka moment.

John Norton-Griffiths Eureka moment

You may think that the only thing linking sewer workers and the front lines was the stench of despair! However, Hellfire Jack had an elaborate plan up his sleeve. He wanted to take his own group of sewer workers, known then as ‘Moles’, to the tunnels on the western front.

Rather than using pickaxes to painstakingly tunnel underground, Hellfire Jack’s Moles utilized a much more efficient technique called ‘clay-kicking’. This involved one man, ‘the kicker’, sitting with his back supported against a wooden cross which was wedged in between the wooden slats forming the gallery that supported the shaft.

His job was to dig a small, sharp spade into the clay in front of him using his legs. Another man, ’the bagger’, would collect any loose sediment. Meanwhile behind them, a third man, ‘the trammer’, would transfer the bags of clay back to the tunnel entrance via a trolley.

clay kicking during world war 1

By taking his clay-kickers to dig tunnels beneath the western front, Hellfire Jack believed that Britain could finally rival Germany in the underground war. After the explosion at the Battle of Givenchy, he wrote to the British government proposing this plan. But, despite his badass nickname, and the increasing threat of German mining, the letter was dismissed.

It took two more months of German mines decimating Allied forces for the British War Office to eventually act. They decided to finally approve Hellfire Jack’s letter, by which point, he knew he had no time to waste. His sewer workers left Manchester immediately, and, just four days later, they were tunneling underneath no man’s land in France.

hellfire jack's men clay kickers manchester france

So, who were these Moles, tasked with the small matter of helping win the war? Sorry to disappoint you if you were picturing small, round men, with gray fur and a pointed snout. They were known as Moles not for their looks, but for their ability to dig.

Many of them were over 40 years old, smaller than 5ft 4, and had no experience of fighting in a war. Considering the maximum age for most soldiers was 40, and the very minimum height requirement was 5ft 3, they weren’t your typical army recruits.

Infantry soldiers would have around nine months of preparation to train, get fit and learn the rules of the army. Yet, the Moles became military men in mere days. Just imagine: one week you’re working your normal job, then days later you’re tunneling under no man’s land in one of the bloodiest wars in human history, that’s quite the career change!

HUMAN MOLES tunnelers WW1

On the face of it, recruiting a bunch of short, old men, with no military experience or training sounds like a surefire way to lose the war. But the Moles had their perks. Clay-kicking was used across Britain for digging sewers, railway tunnels and roads. This meant that a large number of the Moles recruited had prior experience using these methods to burrow underground.

Even more importantly, all the men enlisted knew what it was like to work in the cramped, cold, dark conditions of tunnels. Plus, being a miner or sewer worker meant that you were already likely to be strong, brave, and used to danger.

In contrast, Germany disregarded their miners. Instead, many were sent back home for industry use to aid the war effort. And the German miners that did tunnel underneath no man’s land weren’t given the same responsibility as the Moles. German commanders were unwilling to allow civilian mining engineers to be in charge of military units. It would prove to be a fatal mistake.

Even though the Moles didn’t receive nine months of military training, they still had the spirits of true soldiers. Take one tunneller, William Hackett, for instance. After an enemy mine exploded in the tunnel he and his team were in, they became trapped in their timber supported gallery less than 4ft high and 2 ½ ft wide.

William Hackett trapped in tunnel

After desperately working for 20 hours, the men made a hole through the fallen earth and broken timber. Hackett helped three men to safety through the gap. He could’ve followed too but refused. Instead, he stayed with the fourth man, who was seriously injured. Even as the hole got smaller and smaller, Hackett refused to leave his wounded comrade.

Soon after, the gallery collapsed completely, and neither man was seen again. Undeniable bravery aside, the experience the Moles had also proved invaluable. These were men who were used to the cramped, cold, uncomfortable conditions of mining work, who could work like this for up to 12 hours at a time.

What’s more, there were a huge number of recruits to call on. Miners answered the call from across the UK and British Empire, so by the summer of 1916, the British had 33 tunneling companies at the Western Front, with a whopping 25,000 trained tunnellers made up mainly of volunteers!

Coordinated by the Royal Engineers, the Moles tasked with the Messines mission came from the 171st, 175th and 250th British tunneling companies. There were also two Canadian tunneling companies, referred to as ‘Beavers’, and one Australian tunneling company, called the ‘Diggers’.

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Messines Mines

Their target was the Messines Ridge. It ran north and east of the town of Messines, now known as Mesen, in Belgium. At its highest, the ridge reached 264 feet above sea level, offering a position of immense strategic importance to the Germans, who were able to observe British positions from there.

By capturing the 10-mile-long ridge, the British could straighten their Front Line, allowing them to launch an attack towards Passchendaele, driving German forces further back. But capturing the Ridge wouldn’t be easy. The Germans had held it since November 1914 and had heavily fortified it to mow down any infantry attacks. The only way to take Messines was by going underground.

In the early months of 1916, General Herbert Plumer gave the order for tunneling operations to be carried out under the Messines Ridge. The plan was to dig 22 tunnels under German front lines. Some of the tunnels would need to be more than 125 ft deep and extend more than 2000 ft under their line, meaning it would take more than 6 months to dig out the entire network.

Within each tunnel, a mine would be planted, and then later, detonated, hopefully obliterating the German stronghold on the Ridge. The mass explosion would then be followed by an artillery bombardment and an infantry attack.

british plan to take over the Messines Ridge with explosives

If this plan was successful, the British would take a giant step towards winning the war. But to be victorious, the Moles would have to avoid detection. The only way to do that, was by digging deeper than they’d ever done before. And so, the British used cylindrical steel tubes, known as tubbing.

The tubbing was sunk through the infamous Kemmel Sands, found below ground at Flanders. The Kemmel Sands were unstable terrain that acted like quicksand; if you were to tunnel through it, you’d be at an increased risk of flooding and cave-ins.

But thanks to their steel tubbing, the Moles, Beavers and Diggers were able to reach around 100 feet below ground, far beneath the Kemmel Sands. Here, the earth was mostly made up of clay, the perfect sediment for tunneling.

Messines Ridge tunneling tubbing technique

Unaware of the steel tubbing technique, German forces struggled to find ways beneath the troublesome sands and dig tunnels as deep as the British. Although, it wasn’t just advanced mining technology that helped them. While holding the Messines Ridge gave the Germans the observational advantage, the vantage point also meant that to tunnel to the depths of the British, they had to dig much deeper.

But not only were British tunnels deeper, the Moles, Beavers and Diggers also tunneled much quicker than the Germans. In fact, clay-kicking made the British four times faster at tunneling than the enemy, who were still using pickaxes! Not only that, clay-kicking wasn’t just fast, it was practically silent, unlike the constant thud of German mattocks chipping into the earth.

tunnelling technique comparison

In the tunnels, silence was golden; listening devices such as geophones and seismic microphones were used by both sides to pick up on the slightest vibration. One slip-up could lead to the enemy detecting their tunnel position. If they were heard tunneling underground, they risked having their tunnel blown up by an underground mine planted by the enemy.

This wouldn’t only waste months of excruciating work, it could also entomb the miners in the tunnel! Working in constant silence without any music may be enough to drive you insane, but it was the least of the Moles’ concerns. Unsurprisingly, the tunnels were a claustrophobic nightmare. They were extremely small to avoid detection, not being much taller than 4ft 6 inches.

Even though the Moles tended to be smaller than the typical soldier, it still wasn’t possible for them to stand up straight. As a result, they’d suffer horrendous back issues. And even if they decided to spare their backs and resorted to crawling along the floor, their hands, knees, and nails would be coated in thick clay.

But that wasn’t the only toll this work took on their bodies! Clay-kicking relied on the power of the tunneller’s legs over their slightly weaker arms, allowing the Moles to do more digging in less time. Still, constantly digging out clay from the earth was exhausting. Most of the time, the clay-kickers shared the burden, but even then, they faced grueling 8-hour shifts!

Working up to 125 feet below ground also meant that there was no natural light in the tunnel. With electricity in short supply on the frontline, the Moles had no option but to work by the faint flicker of candlelight.

the moles working condition

But, even worse than the lack of light was the flooding. Digging below the waterline, the tunnels were often flooded, and without pumps the tunnellers had no other option than to work knee deep in the water. The cold, damp and unsanitary conditions that the tunnellers feet were kept in meant that it didn’t take long for the dreaded trench foot to set in.

The constant exposure to these horrific conditions would destroy the blood vessels in the foot, and soon after, blisters and open sores would develop, putting the tunnellers at risk of fungal infections. If left untreated for too long, suffering Moles would need their feet and legs amputated to stop the infection spreading.

Horrendous as that sounds, there was something they feared even more. The Allied tunneling companies weren’t the only ones looking to destroy the enemy from underneath. The Germans also had their own miners, charged with the mission of placing explosives under British front lines, or even to sabotage the Moles’ tunneling mission!

Underground mines, known as camouflets, were used not to blow up enemy trenches, but to cause cave ins to the opposition’s tunnels. If they were unlucky enough to be caught out by an exploding camouflet, everyone in the tunnel would be swallowed by a sea of earth.


An equally harrowing concern for the Moles was the risk of Germans breaking through to their tunnel. If two tunnels met at any point, the miners would be faced with the heart-stopping sight of the enemy just feet away from them.

This would spark brutal and desperate, medieval-like face-to-face conflicts. The tunnellers would attack one another with anything they could get their hands on: shovels, pickaxes, knives, even fist fighting took place! The bloody contest would only end when the enemy was dead, or the tunnel was purposefully collapsed.

Despite the interminable threat of the enemy either bludgeoning them to death, or drowning them in earth, there was an even greater threat: carbon monoxide. Ominously called ‘the silent killer’, carbon monoxide is a colorless, tasteless, odorless gas that comes from the incomplete combustion of carbon, and it’s incredibly poisonous.

Underground specifically, after an explosive action or even firing a single bullet, carbon monoxide would dissipate into the air. Obviously, the bigger the explosion, the more carbon monoxide would be released.

So, when camouflets were detonated, large amounts of carbon monoxide would fill the air. With the tunnels being poorly ventilated, this meant that carbon monoxide could accumulate and spread quickly.

spread of CO in tunnels

The inhalation of carbon monoxide severely reduces the amount of oxygen absorbed into the blood. Even as little as 0.1% carbon monoxide in the air could be deadly. A concentration of 0.2% causes a loss of consciousness in around 25 minutes. In more extreme cases, when the air is concentrated with over 1% carbon monoxide, it leads to unconsciousness after 2 to 3 breaths, and death in less than three minutes.

Hauntingly, this deadly gas claimed the lives of many Moles, but with an unknown number of tunnellers still missing or undiscovered, it’s difficult to know how many miners succumbed to it. Still, many historians believe it was this deadly gas, not the bullets, or bombs, or cave ins, that was the greatest killer of the Moles on the front line.

While carbon monoxide poisoning is believed to be a painless way to pass, that didn’t stop it from being terrifying. The reduced oxygen supply to the brain would lead to palpitations, shortness of breath, and even giddiness. Imagine the horror of being in a dark tunnel and seeing your companions laugh themselves to oblivion, with the knowledge that you’ll be next!

You have probably heard of the phrase ‘canary in a coal mine’; it originated from miners bringing canaries down into coal mines with them. They’re more susceptible to the effects of the gas, so any change in their condition would alert the miners to the invisible gas, giving them precious time to evacuate.

canary in a coal mine origins tunnels ww1

The canary, often known as the ’miner’s friend’, would be kept in a cage by the tunnellers. Though it wasn’t just canaries that were used in this way. Mice and rats were also used to identify the dangerous gas before the miners lost consciousness. If the rodent passed out, or the canary fell off its perch, the men knew that they needed to evacuate, and fast!

Animals weren’t their only saviors, however. The ‘Proto Man’ also came to the rescue of any tunnellers in danger of gas poisoning. Despite the name and the get up, the ‘Proto Man’ wasn’t a World War One superhero. The title comes from the special breathing equipment, called ‘proto apparatus’, used by those sent underground on rescue missions.

It pinched their noses closed and fixed a flow of oxygen from cylinders to a mouthpiece via a harnessed set of tubing. Experienced Proto-Men could last underground for up to two hours searching for any fallen comrades! Good as their intentions were, it's hard to imagine the horror of passing out in a tunnel and opening your eyes to the sight of a ‘Proto Man’!

proto man

Unsurprisingly, the constant anxiety of tunnel life pushed many Moles to breaking point. For this reason, alcohol played an important part in their daily lives. While it may have helped the tunnellers ease their anxiety, drinking at war was a big no-no for commanding officers.

One clay kicker, named Charles Williams, was sentenced to 21 days Field Punishment Number 1 for drunkenness in February 1917. As a result, Williams was tied up to a fixed object, like the wheel of a car or a pole - for up to two hours per day. In total, he would’ve been tied up for over 40 hours!

While getting drunk in an active warzone definitely doesn’t sound like the smartest idea, you’d think that the commanding officers would’ve been slightly more sympathetic to the Moles plight, considering the hellish conditions they were working in. Why would they even take up such a terrible job in the first place?

The love of the King and country will only get you so far but clay-kickers could earn as much as six shillings a day, equivalent to around $22 today, a decent wage for workmen at the time. By comparison, infantrymen in the trenches pocketed just one shilling and three pence, barely making what would be $5 a day.

Moles and infantrymen salary comparison

The disparity in wages, unsurprisingly, led to animosity between infantrymen and the Moles. Those in the trenches even made songs mocking the tunnellers for stealing a living. However, they probably wouldn’t have said that if any of them had spent a few hours in the Mole’s cold, claustrophobic, very damp shoes!

The Battle Of Messines Explosion

In June 1917, mere days before the explosion was planned, the Moles all reached their final positions. In total, 22 mines were planted under the Messines Ridge. Amazingly, only one of the tunnels was discovered and destroyed by the Germans. Work then began transporting the mines to their final locations, and the remaining, undiscovered tunnels were collectively charged with mines.

They didn’t use 10 tons, or 20 tons, or even 50 tons but around 500 tons of explosives! For a little perspective, that’s roughly the same weight as three blue whales! You don't need to be a TNT expert to know that’s enough to make one bloody big boom.

Hours before the attack, General Charles Harington briefed the press and delivered the chilling words: “I do not know whether or not we shall change history tomorrow, but we shall certainly alter geography.” His remark would soon ring true.

In the early hours of June 7th, 1917, the last mine was primed and ready. All that was left to do was to detonate the charges. British artillery stopped firing minutes before the blast as they waited for the otherworldly offensive to begin.

Britse soldaten graven een tunnel om mijnen te ontmantelen nabij Mesen R.E.-s mine and counter-mine Messines Ridge, which dominated Ypres, blown up and stormed, June 7th,-17, RP-F-F06309

The deafening noise of constant artillery fire and shelling stopped, and an eerie silence filled the battlefield. Then, at 3:17AM, the silence was shattered. 19 of the mines underneath the ridge exploded within 20 seconds of each other.

The eruption was monstrous. According to witnesses, the bodies of German soldiers were flung into the air like ragdolls, huge tongues of flame shot out of the earth, and the ground shook ferociously. Many historians believe that the eruption killed around 10,000 German soldiers, with another 7,200 injured, shocked, and captured during the following infantry attack.

Strange as it sounds, the German soldiers who perished were the lucky ones. If being blasted into the air and suffering a bone-shattering fall wasn’t enough, the masses of earth that rained down afterwards smothered many where they lay.

messines ridge explosion

The simultaneous explosions shook the earth for 19 seconds and were so violent that geologists at Lille University, 12 miles away, mistook the tremors for an actual earthquake! Even further away, an insomniac student from the University College Dublin, which is 480 miles from the blast site, reported hearing the boom of the eruption.

It’s difficult to truly determine the power of the blast, but it’s believed that this was the largest man-made explosion at that point in history. And it remained that way until the 1945 Trinity Atomic Weapon Test, the world’s very first nuke. Indeed, this was the biggest blast before atomic bombs!

With most German soldiers either slain or concussed from the explosion, Allied troops swept through the trench lines and reached the Messines Ridge in less than a day. For the next seven days, British forces continued to push forward, taking territory, and repelling German counterattacks.

By the end of the battle, German troop casualties were thought to be 25,000, with 10,000 of those occurring during the mine explosions. Undeniably, the work of the Moles who tunneled under the Messines Ridge helped change the course of the war.

messines ridge explosion death toll

British Captain Grant Grieve claimed that “Never in the history of warfare has the miner played such a vital part in a battle.” While Hermann von Kuhl, a senior German army commander, called the Messines attack, “one of the worst German tragedies of the war”.

Even long after the war, the impact of the Moles work was felt. ‘Der Weltkreig’, the German official history of the war, published in 1939, placed the Messines Ridge explosion second on a list of reasons for the German defeat. That’s a pretty large impact for a group of miners and sewer workers to make!

Back home, these Moles might have been looked down upon. But after that, they were considered some of the most valued troops on the Western Front. It just goes to show sometimes the biggest heroes can come from the most unexpected places!

A 45m-crater caused by an explosion under German positions at Messines, which killed about 10,000 soldiers and shook the ground for kilometres

If you were amazed at the history of the tunnelers that won World War 1, you might want to read this article about the worst roles you could be assigned in WW2 and this article about the worst jobs you could have in a hypothetical WW3. Thanks for reading!

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