Perhaps the pinnacle of craziness in World War I was the tunnel warfare.

Trench warfare on steroids when it comes to dangers, horrors, and suffering that ended with the largest non-uclear explosion in history.

However, it remained a strangely overlooked topic for some reason.

And today, we’re going to correct that.

You’re about to find out what happened when two opposing tunnels accidentally met beneath no man’s land, and how horrific it truly was.

With the introductions of new quickfiring artillery and machine guns, World War I quickly became bogged down into trench warfare.

The most modern armies of the world were not prepared for the evolution of weapons.

Old tactics simply weren’t working anymore, and hundreds of thousands of lives would be lost before that realization finally sank in.

Now, what we call trench warfare came into existence as armies desperately began digging in to protect themselves from new weapons.

But this only created even more problems as when the Western Front was fully established from the North Sea to the Swiss border, neither side could find a way to break through the enemy trenches.

The war simply became two enemy sides, one in front of the other, shelling the life out of each other and unsuccessfully trying to break through in every conceivable way.

Charging across no man’s land quickly proved to be an inadequate solution.

And after every possible tactic failed, soldiers turned to some disturbingly creative ways to outsmart and destroy the enemy.

One of these creative methods was a tactic that goes back to ancient times and was actually quite successful in breaking locks that might be encountered in war, like during sieges.

And the trenches literally became some sort of siege warfare.

If you can’t go over the top and take the enemy position, perhaps the next best thing was [music] digging a tunnel underground, planting a ton of explosives, and giving them a nasty surprise from beneath while you encountered no opposition.

Well, that was the theory.

The reality and practice, as you might expect, were much, much more complicated.

Tunneling was truly a great idea, no doubt, but it would evolve into something dark beyond what I can describe to you, as if the war wasn’t already horrifying enough.

You’ll soon understand what I mean by that.

It is now 1914 and already in the first months of trench warfare, the Germans were the ones to throw the first underground punch and actually show how effective this tactic could be.

In Flanders at Jivvveni, they secretly dug tunnels under British lines and [music] planted 10 small mines of about 50 kilos of explosives each directly beneath an Indian brigade’s trenches.

Then they simultaneously detonated all the mines and immediately followed with an infantry attack to exploit the shock from the explosion.

The whole sector was overrun in mere minutes and over 800 Indian soldiers were decimated in this surprise assault.

Although not nearly close to a decisive blow in the war, this battle alerted and outright terrified Allied commanders to the new threat for which they had no solution, nor tunnelers of their own.

Around the same time, the French had small-cale mining operations around the sum.

But still, no one had anything close to what the Germans had at this point.

However, this was about to change drastically.

Almost immediately after the Germans used tunnels to defeat trenches for the first time, all sides began developing their tunneling tactics, and the game was on.

Underground war quickly began and was split into two major purposes.

Offensive mining, which meant digging a tunnel to the enemy position and planting an enormous amount of explosives, and countermining, which was preventing the other side from doing the same thing to you.

But do you wonder what happens when enemy tunnels accidentally meet each other underground? You’re going to see that as well.

Now, British commanders requested specialist units that would counter enemy miners.

And one idea quickly came to mind.

Who would know better about tunneling than the soon-to-be infamous clay kickers, civilian miners who dug London’s underground tunnels.

If they could use their expertise, the Allies could form an elite core of army sappers and finally [music] solve the trench deadlock.

As 1915 came, the British army quickly formed its first eight tunneling companies of the Royal Engineers.

They were made from regular soldiers, newly enlisted coal miners, sewer diggers, and anyone who knew anything about digging tunnels and had either an excess of bravery or a lack of knowledge about what they were getting into when they volunteered for this job.

They needed them so urgently that some men were literally taken straight from the coal mines in Britain and delivered to the front line within days.

Very soon, the British had expanded to over 30 tunneling companies with 21,000 tunnelers working on projects under the Western Front.

Canada formed three while Australian and New Zealand companies arrived later at the peak of tunnel warfare.

The French also developed their sappers while the Germans and Austrohungarian armies were following close behind.

Everything was set to transfer the combat underground which would give it some really unique spice of horrors that you can’t find in any other form of combat throughout history.

Very soon after the forming of tunneling units, the British would test them on a large scale for the first time.

Royal engineers planted a series of six huge mines under the German-h held Hill 60 near Epra, a heavily defended position that couldn’t be captured on the surface.

When everything was set, all the mines were detonated in unison, followed by an immediate infantry charge.

Hill 60 along with its unfortunate German defenders was literally blown apart and British infantry seized the cratered remains with ease.

They would actually lose it in counterattack soon after, but the sheer effectiveness in obliterating previously untouchable positions just pushed every nation into tunneling even more.

And throughout 1915, underground warfare intensified across the western front.

Now, although the British started after the Germans in this game, they quickly caught up and surpassed German techniques.

You see, the British used the so-called clay kicking technique, whereas the Germans didn’t know anything about this.

Clay kicking was really effective in regions where the earth was made up of clay, like it was in Fllanders where the majority of tunnel warfare took place.

The British would dig deeper than the Germans.

First with a vertical tubed shaft where steel cylinders would jack down through the soft quicksandy ground until they hit a deeper layer at around 30 m where the blue clay was, which was much easier and safer to dig.

Then they’d start tunneling horizontally towards the enemy side, digging at a slight upward angle so water would flow back and keep the digging point dry.

This, however, came with the danger of gases accumulating in tunnels, but you’ll hear more on that when describing how the tunnels really looked like.

This technique gave the British several key advantages.

A [music] three-man team would work together.

The kicker sat with his back against a wooden support and dug out the clay by kicking in a spade-like tool and slicing pieces of clay.

The bagger would collect them, fill the bags, and pass them to a trammer, who would take them out of the mine and bring back support wood.

This way, digging was silent as they wouldn’t be hitting with pickaxes like the Germans did, and clay transferred sound much less than other types of soil, so they were much harder to detect by listening.

It was also much faster.

Clay kickers could dig an average of 8 m per day, whereas the Germans could only manage two.

The British also used special wooden support timbers that would be set every 9 in to keep the tunnel stable.

It was ingeniously designed to be mounted in absolute silence.

Unlike the Germans, this system didn’t need nails or screws that could reveal their position.

Instead, the timbers were pre-cut and just put together inside the tunnel like Lego.

The boards would clip into each other and the moisture would cause the wood to swell and lock in place without the need for any hammering.

Every little thing had to be thought of if you wanted to live.

For example, where would you dump all the earth you were digging out? You could fill sandbags and use them as protection for trenches on the surface.

But then there was a problem.

If the enemy saw the type of soil in torn sandbags and it was blue clay, they’d immediately know that there was a mining operation nearby.

And they do everything to make your life even more difficult than it already had to be.

These sections of suspected mining operations received a much larger portion of shelling and even raids to locate them.

So the ground units hated when tunnelers were working near them.

Before we go into what happens when two opposing sides meet in tunnels underground, let’s first describe the atmosphere inside them.

So you’ll have another layer of horror in your mind when the actual fighting takes place down there.

Now working in a tunnel, as you might imagine, was everything opposite to a safe and comfortable experience.

You’ll understand why they got paid six times more than a frontline private.

Being buried alive, drowned or asphixxiated were just one part of the job description.

Besides, of course, claustrophobia and unwanted guests that might crash the party.

Tunnels were usually about 4 ft high by 2 1/2 ft wide, which was barely enough for a man to work crouched.

Shifts were between 6 and 12 hours.

And conditions were catastrophic.

[music] Wet, cold, dark, cramped, with constant risk of cave-ins, gas poisoning, enemy countermining operations, or hitting an underground water line that could fill up your tunnel in seconds.

Foul air and humidity in such a cramped space was described by veterans as being in a coffin that sweated.

Men worked with candles or oil lamps as their only source of light, and they watched the flame carefully, as it would also indicate the lack of oxygen in the tunnel.

Gas was always a danger because it would linger down from the constant shelling and explosions outside or even worse from gas attacks.

Chlorine and phosgene were heavier than air and fumes could sink into shafts and build up in the tunnels.

So, the entrances usually had to be air sealed to prevent this.

Tunnelers often use small animals like mice or canaries as living gas detectors.

They’d show signs of poisoning first and warn the men to leave the tunnel immediately.

Then there was the danger of the tunnel entrance being hit by artillery or even captured by the enemy on the surface.

For [music] example, French artillery once hit the German Winterberg tunnel entrance, which collapsed and sealed inside more than 250 men, out of which only a handful somehow managed to escape in the days that followed.

The rest are still buried somewhere beneath the ground.

There were also raid operations to capture tunnel entrances to [ __ ] enemy mining operations.

The Germans like to do this to the British and were successful a couple of times.

Tunnelers would emerge only to realize the entrance was now in [music] enemy hands, or even worse, that it had been collapsed with explosives and they were now trapped underground.

Meeting in the tunnels.

It was rare but not impossible for enemy tunnelers to meet underground as there were miles of tunnels dug into specific front sections.

Sometimes this happened on purpose, other times not.

[music] As the tunnels were small and narrow, fighting with rifles or any standard weapons was impractical.

So tunnelers used their digging tools or speciallymade weapons like swordoff rifles, revolvers, or knives for savage melee combat in just a few cubic feet of darkness deep underground.

Now imagine that all of a sudden the earth collapses and reveals an enemy tunnel.

Maybe it’s empty, maybe not.

If there’s someone inside, you’d now be fighting the enemy tunneler in a cramped, pitch black tunnel with your bare hands.

And I think that this experience couldn’t ever be truly described with words.

Just imagine the fight for your life in conditions already terrifying enough to be in, let alone to fight.

I don’t know if there’s any other form of life on Earth that goes this far in order to destroy other individuals of its own species.

When an enemy tunnel was discovered, tunnelers would usually go in to inspect it, sometimes even reaching the enemy trench where the entrance was.

if the tunnel had been abandoned.

As the effectiveness of mining missions terrified every soldier in the frontline trenches, they desperately tried to find a way to detect tunnelers digging toward them.

At first, these were improvised listening devices like oil drums filled with water, then staring at the surface of the water to see vibrations or shoving a stick into the ground and biting onto it with their teeth to feel vibrations.

But soon this evolved as well.

Stethoscopes and eventually geophones were introduced to detect noises in the ground up to 160 ft away.

Dedicated listeners mann them around the clock to determine direction and guide a counter operation to dig a tunnel underneath and place an explosive charge called a camoufl either to collapse the enemy tunnel or to detonate it in front of it and make the ground unstable for further digging.

This could of course also happen to you if the enemy detected and intercepted your own tunneling operation.

However, they weren’t always successful in detecting enemy tunnelers in time, as the diggers were ultra careful to make as little noise as possible.

Listeners said that the scariest part wasn’t hearing enemy tunnelers dig, but when they could hear them for days, and then suddenly there was silence.

That silence could easily mean they had successfully planted a mine and retreated, just waiting for the right moment to detonate it.

And while we’re at detonation, let’s explain how that looked and how mining was used in practice.

Before the enormous mines that would later be detonated and still stand as the largest non-uclear explosions in history, there were smaller ones.

At first, both sides used gunpowder in early mines, but the results weren’t impressive because of the way it exploded.

Then the British adopted aminal, which performed much better and had that lifting power.

It was made from about 70% ammonium nitrate, 20% [music] TNT, and 10% aluminum powder.

This way, it created a massive volume of gas and heat that would throw thousands of tons of earth into the air and create huge craters.

It was cheap to produce in large quantities and more stable than pure TNT.

The problem was it absorbed moisture, so it had to be carefully bagged in waterproof sacks.

They were then detonated by electric detonators with wires leading to a safe distance.

For example, during the Battle of Orers’s Ridge, several mines, each holding a few hundred pounds of explosives, were fired at zero hour in coordination with infantry units to disrupt enemy defenses.

After the explosions, obstacles and key enemy positions, were blown into the air, leaving behind huge craters.

Infantry would then sprint to capture and defend these craters in savage fights.

However, the size of the underground networks and mine charges grew ever larger as tunnelers refined their techniques.

By 1916, underground warfare had reached new extremes of scale and ferocity.

Tunnelers on both sides were now quite literally fighting a war beneath the war.

The Battle of the SO would mark a turning point in mine warfare.

British Royal Engineer tunneling companies worked for months underground in complete secrecy.

On July 1st, 1916, at 7:28 a.

m.

, 2 minutes before the arranged infantry assault, they detonated eight huge and 11 smaller mines under German positions, amounting to tens of thousands of pounds of explosives.

The blast tore the earth open and created craters up to 65 ft deep and more than 300 ft across.

German strong points along with their defenders were hurled into the air.

British troops then charged forward to capture the crater rims.

Although the SOM showed the enormous potential of these huge mines, it also showed the need for better coordination with infantry to fully exploit [music] the chaos the mines created.

At this point, these explosions were the largest human-made blasts in history.

But they were about to be outdone the following year at Messen, where the tunnelers would really show what they could do.

The pinnacle of World War I tunnel warfare came in June 1917 at the Battle of Messen Ridge.

These were heavily defended German positions that had been held firmly since 1914.

For the planned offensive to be successful, this specific position had to go.

However, the terrain strongly favored the Germans, and the Allies found out through many bloody and failed attempts to capture it that this wasn’t going to be an easy job.

So, after 18 months of secret preparation, 21 huge mines were planted by British and Commonwealth tunneling units beneath those untouchable German positions.

They had actually prepared 26 mines, but some had to be abandoned after German countermining flooded them.

Some tunnels ran for nearly 800 yards, and the combined length of tunnels dug for this operation was over three miles.

All of this was done in absolute silence, avoiding German counter sappers and navigating dangerous ground riddled with water pockets.

The Germans knew mining operations were underway, but Allied tunnelers had gone deep underground into clay layers where they were much harder to detect.

[music] They even dug faint tunnels to deceive the Germans and hide the real ones deeper down.

Across the front line, the total mine belt carried around 450 tons of explosives, all ready to be detonated.

On June 7th, 1917, at 3:10 a.

m.

, within roughly 20 seconds, 19 mines erupted along a line of nearly 6 m.

The whole ridge was lifted hundreds of feet into the air and then came crashing back down.

As the dust slowly settled, the enormous craters revealed what was left of the once impregnable German defenses.

Thousands of defenders were simply gone.

Either blown from the face of the earth or intombed deep below it.

Estimates range between seven and 10,000 German soldiers killed in the detonations alone.

Many of them hiding in deep dugouts that had protected them from artillery bombardment.

But nothing could protect them from this enormous set of explosions that literally changed the local geography.

Infantry divisions then ran over the devastated landscape with almost no opposition from the other side with surviving Germans either surrendering in complete disorientation or being overrun by Allied troops advancing under a creeping barrage.

The operation was a success because of the close cooperation between ground and underground units and the tight coordination with artillery to exploit the breaches the mines created and to correct the mistakes made earlier at the SO.

Some mines actually weren’t detonated.

One famous example exploded decades later in 1955 when lightning struck and triggered the charge, detonating in a Belgian field and killing a cow.

Several more large mines remain underground to this day.

Perhaps they are still waiting for the wrong spark in the wrong place to show us what they are capable of.

The craters from Messine still stand to this day and you can visit them in Belgium.