WW1 Underground Tunnel Warfare: Miners, Mines and Messines 1917

Underground tunnel warfare in World War 1 was the war fought beneath no man's land: military miners dug galleries under enemy trenches, packed them with explosives and blew the position up together with its garrison. The practice peaked at Messines in Belgium on 7 June 1917, when the British detonated 19 mines holding roughly 450 tonnes of ammonal at 03:10 in a single coordinated blast. Around 10,000 German soldiers died in seconds, and the roar was recorded in London more than 200 kilometres away. This article is for anyone interested in World War 1 history who wants to understand how armies broke a front that no frontal assault could crack.

Key takeaways

• Mine warfare appeared exactly where the surface front froze: if you cannot go around a position, you go under it.
• British tunnelling companies numbered about 25,000 men by 1916; in that year alone the British fired 750 mines and the Germans 696.
• The largest mining operation of the war was Messines Ridge, 7 June 1917: 19 charges, roughly 450 tonnes of explosive.
• The craters are still there. Lochnagar Crater in France is about 91 metres across and 21 metres deep.
• Modern strategy games inherited the problem rather than the tunnels: how do you break a position that infantry cannot take head-on?

Why armies went underground

By the end of 1914 the Western Front was one continuous trench line from the North Sea to the Swiss border. There were no flanks left to turn. We covered how that deadlock formed in our piece on trench warfare in World War 1.

When a front freezes, a commander has three options: more artillery, new technology, or a different dimension. The first two produced multi-hour creeping barrages and the tank. The third dimension was depth.

The idea itself was ancient. Sappers had undermined fortress walls since antiquity: dig a gallery under the wall, prop it with timber, burn the props, and the wall collapses into the void. World War 1 only changed the scale. Instead of a wall, a kilometre of trenches. Instead of fire, hundreds of tonnes of industrial explosive.

Who did the digging: miners, not soldiers

Ordinary infantry could not do this work. The British command took an unusual route and recruited civilian specialists, above all the "clay kickers" who had bored sewer tunnels under Manchester and London.

The technique looked like this. The worker lay on his back against an inclined wooden cross, set both feet on a specialised spade and pushed the clay out using his own body weight. The arms barely move in that position, so the tool barely makes noise. Silence was the entire job: a single pick strike gave away the bearing of a gallery to enemy listeners.

What made the tunnelling companies so valuable:

• They brought industrial experience with wet ground, timbering and ventilation that the army simply did not have.
• They worked faster, advancing several metres a day where regular sappers stalled.
• They could work quietly, and in mine warfare silence was survival.

Conditions were appalling even by front-line standards. Galleries ran at roughly 25 to 36 metres below the surface, the longest exceeded 650 metres, air was pumped by hand bellows, and the real enemies were collapse, flooding and suffocation rather than bullets.

Counter-mining: listening to the earth

The moment one side started digging, the other started listening. Geophones were used, along with a cruder trick: a sapper pushed a stick into the gallery wall, clamped it between his teeth and picked up the vibration through the bones of his skull.

Once an enemy gallery was located, the answer was a camouflet: a charge sized not to blow up the trenches above but to collapse the hostile tunnel underground. Sometimes two shifts broke through into each other and the fight continued in the dark, in a tunnel lower than a standing man.

The result was an underground front running on its own calendar. Months could pass without an attack on the surface while someone blew someone up every week below. The clearest example is the Butte de Vauquois in France, where 519 detonations were recorded between 1915 and 1918 and the summit of the hill was lowered by roughly 18 metres.

Messines, 7 June 1917: the explosion heard in London

Messines Ridge, south of Ypres, gave the Germans observation over the British lines. Storming it frontally meant repeating the Somme. So preparation started almost two years before the attack.

The scale of the operation:

• Tunnelling companies drove more than two dozen galleries under the German positions along the ridge.
• Roughly 450 tonnes of ammonal were placed underground, split between charges of different sizes.
• At 03:10 on 7 June 1917, 19 mines were fired almost simultaneously.
• German losses from the blast itself are estimated at around 10,000 men.
• The shock and the sound were registered in London, some 230 kilometres away.

What followed was rare for World War 1: the infantry took the ridge within hours, because there was almost no one left to hold it. Messines remains one of the few episodes where preparation produced a near-perfect result, which is why it is still studied alongside the war's largest operations, reviewed in our guide to the biggest battles of World War 1.

The story had a late sequel. Several charges were never fired. On 17 June 1955 lightning struck one of them and a forgotten mine detonated 38 years after the battle. No one was hurt.

The craters still on the map

Mine warfare left the most durable scar of any weapon of its era: holes that a century has not filled in.

Lochnagar Crater

Fired at 07:28 on 1 July 1916 at the opening of the Battle of the Somme, near the village of La Boisselle, with a charge of about 27 tonnes of ammonal. The crater today measures roughly 91 metres across and 21 metres deep. It was bought by a private owner and is preserved as a memorial.

The mountain front

In the Alps and the Dolomites the enemy was rock and ice rather than clay. Italian and Austro-Hungarian engineers drove adits through limestone, and on the Marmolada glacier the Austrians carved an entire network of passages inside the ice to shelter from shellfire and cold. We covered that theatre separately in our article on the Italian Front.

Why tunnel warfare disappeared

Messines was both the peak and the end of mine warfare. Three reasons stand out.

First, the operation needed about two years of preparation on one sector. That only works while the front stands still.

Second, in 1917 and 1918 the war became mobile again. Tanks, stormtroop tactics and aircraft restored movement, and a tunnel cannot keep up with a moving front. We traced that shift in tempo in our piece on World War 1 tanks.

Third, artillery grew so heavy that siege guns and railway mountings delivered a comparable effect in hours rather than years. More on that in our article on World War 1 artillery.

What carries over into Frontkrieg

Frontkrieg has no underground galleries, but it has the exact problem those galleries existed to solve: a position frontal assault cannot take, and the price of the time spent preparing one that can.

Three moves that do the job a tunnel used to do:

• Artillery as preparation. Guns shell a province from the neighbouring one and break infrastructure, not just the army standing on it. Our guide on destroying enemy buildings covers how to knock out factories and railways.
• The fortress as an answer. A fortress upgrades to level 5, and from level 3 it hides the size of its garrison from enemy reconnaissance, so the attacker plans blind. That is precisely how the German positions at Messines worked until they were found from below.
• Logistics instead of depth. Railways sharply speed up army movement through a province, and a prepared strike from the right direction is usually cheaper than any head-on assault. We traced the historical parallel in our piece on railways and the Schlieffen Plan.

The lesson of Messines for a player is simple: fronts are broken by preparation the enemy does not know about, not by the amount of infantry thrown at them.

Frequently asked questions

Why were tunnellers so respected in WW1?

Because nobody else could do the job. Driving a silent gallery through wet ground more than 25 metres down required mining skills, timbering and ventilation knowledge the army lacked. British tunnelling companies numbered around 25,000 men and were paid more than ordinary infantry.

How many mines were blown at Messines?

At 03:10 on 7 June 1917 the British fired 19 mines with a combined charge of roughly 450 tonnes of ammonal. Several additional charges that had been laid were never used, and one of them detonated after a lightning strike in 1955.

Are there unexploded WW1 mines left?

Yes. Some charges under Messines Ridge are still underground, because their exact position and condition are unknown and digging the explosive out is more dangerous than leaving it alone. Those areas are mapped and monitored for that reason.

Is tunnel warfare still used?

Undermining fortifications the way it was done in 1917 has disappeared, because fronts rarely stand in one place for years. Underground structures as shelters and supply routes remain part of military practice, so the underlying principle of moving the fight into a dimension the enemy does not control is still very much alive.

Conclusion

Underground tunnel warfare in World War 1 was the answer to the deadlock of the trench front: if you cannot go around a position, you go beneath it. Messines on 7 June 1917 showed the method at its absolute limit - 19 mines, roughly 450 tonnes of explosive, a ridge taken in hours, and a bill of two years of digging.

If you want to test that logic yourself, Frontkrieg starts a new match every day: up to 500 players and 70 AI nations on a 4,800-province map, free to play with no pay-to-win, straight in your browser. Open the lobby and try taking a fortified province with preparation instead of a frontal attack.

More history and mechanics breakdowns are in the Frontkrieg blog.

Source: World War I - Wikipedia