In World War I, whole companies of men were assigned to burrow beneath enemy soldiers, then blow them sky high.

They called themselves moles. Most were short, wiry men from the mines of Great Britain and Canada and Australia. Their special talent was the ability to kick rapidly and silently through the moist blue clay beneath the fields of Flanders. As soldiers, they chafed at rules and regulations. But as tunnelers, they were the best in the world. Even the Germans admitted that. And though the Germans pioneered the use of mining during World War I—a German mining engineer was in fact called a pionier—the British quickly caught up, and then surpassed their enemy’s efforts.

Mining is a strange form of warfare. Men burrow underground, digging toward a target in the enemy’s lines—usually a fortified strongpoint. When directly beneath it, they fill a chamber to the brim with high explosives, run a wire back to the safety of a command post and, when the moment is nigh, plunge the detonator. The result is a huge spume of mud and bone issuing from the rupture in the earth, leaving a crater that might be more than 200 feet across and 50 deep.

Germans fired the first mines of the Great War on December 20, 1914. There were 10 in all, along a 1,000-yard front at Festubert, in French Flanders. The German pioniere had tunneled under lines held by a British corps of Indian soldiers. The explosions killed many outright. Others fled to the rear, followed as they ran by a barrage of enemy mortar fire, and behind that, charging German soldiers.

The impact upon morale was devastating. Troops in the trenches could often hear their enemy digging beneath them. Even more terrifying was the worry about when they might detonate the explosives. In a minute? An hour? A day? A week? Soldiers were accustomed to artillery barrages. They could hear the shells coming. They could take cover. The same was true of frontal assaults. They could see the enemy storming across no man’s land. They could fire back. They could, if they had to, fall back. They felt as though they had some control over their destiny. But with underground mines there was no warning.

The earliest use of military mining is thought to have been around 800 BC, when the Assyrians used tunnels to breach their enemy’s fortifications. Digging to a point just under the walls, they propped the cavity with heavy, pitch-coated timbers, and then filled it with brush and other flammables. Right before the assault, the Assyrians set the wood on fire. As the supports burned, the wall collapsed into the pit, creating a gap through which soldiers could rush the fortress.

The English were early adopters of mining. In 1215, King John laid siege to Rochester, and put his sappers to work to undermine the castle. To flammable materials his majesty added 40 slain bacon pigs, whose lard made the fire burn hotter, cracking the wall’s foundation.

By the middle of the 15th century, many European nations were using gunpowder in artillery and shoulder weapons, and not long after, military mining. Powder was first used successfully at Naples in 1495, when besiegers exploded a mine beneath the city’s magnificent Castel Nuovo. Among the engineers involved in early Italian efforts was a prolific designer of military machines, one Leonardo da Vinci.

For the next 400 years mining was in common use by armies around the world. During the American Civil War, Union general Ulysses S. Grant employed it at the sieges of Vicksburg and Petersburg—unsuccessfully, it turns out, because the Union attacks that followed were poorly coordinated. Over the centuries, the explosives got more powerful and the techniques more refined, but to place the charges beneath the enemy still required tenacious men willing to claw away underground at the mud and chalk and clay.

The German mining offensive along the Western Front in December 1914 brought immediate calls from British commanders for retaliation. But in those early days of the war the British Expeditionary Force (BEF) was ill prepared and ill equipped for the job. By remarkable coincidence, just five days before the first German mine attack, the irrepressibly energetic Major John Norton Griffiths, a member of Parliament and founder of the 2nd King Edward’s Horse, sent a letter to the War Office suggesting he form a unit—a “handful of moles,” he called them—to dig tunnels and place mines at the front. A tall, handsome adventurer, Norton Griffiths had joined the Royal Horse Guards at age 17 but left after a year for South Africa. He tried sheep farming. He tried gold mining (where he learned all about tunneling and explosives). And when the Second Boer War broke out in 1899, he tried the army again, then returned to the United Kingdom to make his fortune in engineering.

The moles he had in mind in 1914 were excavators under contract with his engineering firm to construct a sewer system in the city of Manchester. These men had a special faculty for digging. They used a simple technique called clay kicking. The mole lay at an angle against a wooden plank at the front of the workings. With his feet he pushed an odd-shaped shovel (called a grafting tool) into the clay. The spoil was then passed back to others for removal. It was quick. It was quiet. And Norton Griffiths knew it was the best way to mine and countermine the enemy. But his suggestion languished for several weeks—during which the Germans fired three more mines.

Finally, on February 12, 1915, Norton Griffiths was invited to the London office of the commander in chief, Field Marshal Horatio Herbert Kitchener. The major explained his moles and their clay-kicking methods, even flopping onto the floor to demonstrate that technique.

Lord Kitchener, hounded by his generals at the front to find a way to combat German mining, was so pleased with what Griffiths told him he sent the major to the battlefront that very night to reconnoiter. Within days, the War Office had authorized the formation of eight tunneling companies.

As soon as Norton Griffiths returned to London, he began recruiting men—pulling the first 18 from the sewer job. As one officer recalled, “On Thursday, February 17th, these men were burrowing under Manchester: on Monday, [the] 21st they were working underground in [France].” He signed up dozens more civilians. And the ranks of existing army units were canvassed for soldiers with mining experience.

One of the first groups, 171 Company, was taken to a place called Hill 60 in Belgium. This little rise in the otherwise gently undulating ground east of Ypres was nothing more than a 50- foot pile of earth excavated from a nearby railway cutting. But its slight elevation gave whoever held the mound a distinct tactical advantage.

On March 8, 1915, the company—commanded to drive three tunnels under the German lines—began to dig at Hill 60. Five weeks later, on April 17, the engineers fired the first successful British offensive mines of the war. The trio of blasts rent the hummock, sending debris 300 feet into the air. BEF troops rushed in, took, and held the position. The Germans counter attacked relentlessly, day after day, finally resorting to chlorine gas to flush out the tommies. That was on May 5. They would hold the hill for another two years, despite repeated and bloody attempts by the Allies to dislodge them.

By midyear the British mining effort had made great strides— and Norton Griffiths was frequently spotted cruising the battlefields in his wife’s Rolls-Royce, handing out cases of fine whiskey and vintage port to those he deemed deserving. Many of the British mines were defensive in nature—countermines— and the Germans still had the initiative. But before 1915 was out the British had 20 tunneling companies beavering away on the Western Front, each with some 550 men.

Tunneling and mining was a complex business. The composition of the ground was critical. In the Somme, 50 miles south of Flanders, the soil was a hard chalk that was easy (though noisy) to cut through. But Flanders featured a distinctly uncooperative geology. First came a thin layer of topsoil, then a stratum of moist clay. The next layer was the devil’s work— 40 or 50 feet of what is called running sand—a thick slurry of constantly shifting quicksand. Finally, below that was an impermeable barrier of blue clay, upon which all the other strata essentially floated. (It really was blue—and when exposed to the air, a bright blue.)

Getting a shaft down to the clay proved difficult for the British and, in particular, the Germans, whose equipment and methods were less evolved. But in mid-1915 the moles worked out a solution. As they dug through the running sand, they sank steel caissons to form a waterproof shaft. Once those cylinders, known as tubbing, hit the clay, the miners could start kicking toward their objective. In decent conditions they could excavate 20 to 30 feet a day, forming tunnels that were typically 41⁄2 feet high by 21⁄2 feet wide. Both sides used standard box timbering to line the horizontal passages called galleries. The German pioniere tended to hammer their timbers into place (a noisy operation); the moles used precut mortised “setts” which snapped (quietly) together without fasteners.

Once under their objective, the miners dug the charging chamber. It was the size of a small room, and it too was lined with boards. They then carefully fitted their cache of explosives in 50-pound rubber bags or metal tins—hundreds or even thousands of them. At the beginning of the war the British most often used gunpowder and guncotton, mainly because these were easy to handle.

But soon a new and far more powerful explosive—ammonal—became available. Made from ammonium nitrate, aluminum powder, and TNT, it was very stable and cheap to make, and most important, packed twice the wallop of powder.

When the charge was in place, the miners wired the detonators; there were usually several, on two or three separate circuits. They then sealed the end of the tunnel with a yards-thick belt of sandbags. This procedure, called tamping, was to ensure that the force of the explosion would go up toward the surface, not back through the gallery. Later in the war some mines were so powerful they required hundreds of feet of tamping.

Hazards in the tunnels were manifold: collapse, flooding, countermining, gas. The last was the most dreaded. The gas wasn’t the kind used on the battlefield—not phosgene or mustard or anything exotic—but simple carbon monoxide. Odorless and colorless, it could rapidly disable or kill the moles before they even knew what was happening.

That’s where canaries came in: Their smaller, more sensitive physiology reacts more quickly to the presence of carbon monoxide. They were placed in cages at the face of the tunnel and if they suddenly fell off their perches, the miners knew gas was present and could safely evacuate. Like grafting tools and sandbags, canaries were standard Royal Engineers issue.

When British moles got trapped underground by gas or started to become asphyxiated, a “Proto man” would be sent in to save them. He was a mole who was also an expert in mine rescue. His nickname came from the heavy self-contained breathing apparatus he wore—a “Proto set” with the filtering material Protosorb—that enabled him to work in gas-filled tunnels for up to 45 minutes. The teams of Proto men on duty in each shaft gave the miners some peace of mind.

To track the movement of enemy tunnelers, miners kept an ear out for them. But it wasn’t until early 1916 that the moles had instruments that could take advantage of the fact that sound travels faster through the earth than in air. That was when Norton Griffiths introduced a device he had discovered in Paris: the geophone, a pair of mercury-filled mica disks with earpieces. By placing the geophone against the wall or floor of a tunnel, well-trained listeners could discern the direction and distance of sounds. Shoveling could be heard up to 70 feet, talking up to 50 feet. To their eternal regret, the Germans were energetic excavators and avid conversationalists. The moles sometimes had a dozen or more listening stations at three or four levels in a single tunnel system. One sound they all feared was silence, for it often meant the enemy was ready to fire a charge.

On occasion—often enough to keep everyone on his toes— opposing forces would come upon the enemy’s galleries. At the very least, the trespassers would explore the tunnel, usually leaving behind a small charge to destroy the workings. Sometimes the two sides would meet, and there would be a regular donnybrook in the darkness, each side armed with fists, knives, pistols, and hand grenades.

In one such incident in September 1916, a young Canadian lieutenant, John Westacott, and his sergeant were checking tunnel entrances in the trenches near Hill 60 when they rounded a corner and walked into a company of German scouts. “Truth dawned with a shock like a kick in the stomach,” he recalled. The pair turned tail and ran deeper into the mine, the Germans close on their heels. Shots soon rang out. It “was a frightful inferno of noise, smoke and confusion.”

When all else failed, the lieutenant’s moles resorted to slashing at the enemy with their daggers. Then Westacott heard a grenade land at his feet. The explosion ripped off his left arm and threw him unconscious to the floor. The melee in the mine continued as his men dragged him to safety. After 24 hours of desperate fighting, the Canadians emerged victorious, but the cost was dear. Westacott’s company of 80 sappers had been reduced to 20.

Early in the war, well before his tunneling companies made much of an impact, Major John Norton Griffiths had an earth-shaking idea. Literally. Using a series of six big mines, he wanted to, in his words, create an “earthquake” that would straighten the Ypres Salient—a deep German-held bulge into British lines around the devastated city of Ypres. He proposed that the Germans be blown cleanly off the Messines Ridge along the four-mile front from St. Eloi to Messines, followed by a coordinated infantry assault to take and hold the newly cratered land.

In May 1915 he presented his audacious scheme to his superior, Brigadier George H. Fowke. The general turned him down cold. But in January 1916 Fowke and Norton Griffiths were summoned to a meeting of the BEF’s ranking generals to explain the earthquake strategy. After some hesitation the high command approved the plan. They wanted the Flanders mines readied by July, for use in a diversionary attack in concert with what was touted as a war-winning Anglo-French offensive in the Somme.

The tunneling companies got to work. Instead of the six mines Norton Griffiths had proposed, there would be 25, covering an eight-mile front. Secrecy was crucial. This meant shafts had to be deeper and galleries longer. In the cluster of mines at Kruisstraat, near the center of the bulge, the main tunnel stretched nearly 2,200 feet. By the end of June 1916 most of the mines on Messines Ridge had been driven and charged.

But the attack was postponed; the delay, it turned out, lasted a year. So the mines sat, deteriorating a little each day and vulnerable to discovery by the Germans. As one tunneling officer later wrote, “The constant and anxious task of keeping the mines intact was far more nerve-racking than actual mining. Would the dampness cause a short circuit? Had the chambers collapsed? Would a chance enemy blow wreck a gallery? These, and a hundred other such thoughts tormented the tunnelers.”

In August the moles lost one of their biggest mines to German countermining. Known as Petite Douve, the 865-foot tunnel had been filled with 50,000 pounds of ammonal when an enemy camouflet (a mine with a reduced charge) wrecked hundreds of feet of gallery. Fearful that further work would alert the Germans to the grand strategy, the British tunnelers reluctantly abandoned the mine.

At the close of 1916 the tunneling companies could look back upon a very busy year. They had fired 750 mines and camouflets—more than two a day. The pioniere had responded with 696 of their own. The British were wresting away the mining initiative from the Germans, and would never lose it.

Early in 1917 BEF commander General Douglas Haig resurrected his plan for an offensive along the Ypres Salient in Flanders, intending to launch it by firing the Messines Ridge mines. He tapped the Second Army’s able and meticulous General Herbert Plumer to lead the assault. When Plumer and his staff finished their planning, they announced they would need only 19 of the 25 charges.

Then the pioniere struck again.

There was a place midway on the ridge called Spanbroekmolen, a deep and strong German bunker manned by crack troops. From their vantage point they could watch every move the British made. And deep beneath that bunker sat a huge British mine, charged with 91,000 pounds of ammonal. The Germans, suspecting it was there, blew a powerful camouflet on March 3, 1917, that nearly destroyed the 1,700-foot tunnel.

Unlike at Petite Douve, the BEF engineers decided Spanbroekmolen was too important to give up. They immediately started driving a parallel gallery in an effort to reach the cache of explosives. Every day for three months the moles kicked furiously through the blue clay. Topside, the preparations for the assault had by then reached fever pitch: The opening of the offensive was set for precisely 3:10 a.m. on June 7.

All was in readiness. All except Spanbroekmolen.

Right up through June 6 the moles toiled to restore the huge mine. Finally reaching the tins of ammonal, they found the firing circuits damaged beyond repair. The officer in charge, Major Henry Hudspeth, decided to bypass the tangle of frayed wires and hook up a dynamite priming charge to the electric lighting circuit. It was risky, and he wasn’t at all sure it would work, but with the clock ticking down it was his only hope. His moles finished just hours before zero.

In the previous seven days, British artillery had pounded the German fortifications and trenches along the front with more than three million shells. Said an infantryman, “The noise was too terrible to describe.”

The salvos stopped suddenly at 3:06 a.m. on June 7, and it got very quiet along the Messines Ridge. “Perfect stillness,” wrote one soldier. Birds could be heard singing. It spooked soldiers on both sides.

Four minutes later that stillness ended abruptly. Eighteen mines went up in spectacular synchronicity. All except Spanbroekmolen. As chaos erupted around him, Major Hudspeth fiddled desperately with his detonator. Finally, 15 seconds late, the equivalent of 200,000 sticks of dynamite erupted under the German bunker. Hudspeth’s jury-rigged circuit had worked. He felt “profound, profound relief.”

The pillars of fire awed all who witnessed them.

“In the pale light it appeared as if the whole enemy line had begun to dance, then, one after another, huge tongues of flames shot into the air, followed by dense columns of smoke,” recalled one mole.

The correspondent from the London Daily Mirror wrote: “The air shook, as the earth shook, and where the earth and air met incredible explosions set the world on fire.” His rival from the Times of London echoed the thought: “It was terrifying as a spectacle, and what was more terrifying was that the earth shook like a house of cards. It quaked like jelly. There is nothing to which to compare it.” A German after-action report noted: “The ground trembled as in a natural earthquake, heavy concrete shelters rocked, a hurricane of hot air swept back for many kilometers. The effect on the troops was overpowering and crushing.”

The bold Norton Griffiths scheme of “earthquaking” the Messines Ridge—25 months in the making—had come to a devastating conclusion. But the major was not around to witness it. He had left the mining corps more than a year earlier to pursue other schemes, the most audacious of which was his successful destruction of Romania’s rich oil fields before the Germans tapped them.

No sooner had the sound of the explosions died than another terrific din enveloped the ridge as British artillery opened back up— the signal for the tommies to go over the top and attack the now pulverized German positions. Within three hours all of General Plumer’s initial objectives had been won, and with fewer casualties than expected. The complex mining-artillery-infantry assault was considered a major success.

This was the biggest manmade explosion in history; the 19 mines had been charged with nearly a million pounds of explosives. Some 7,000 German soldiers were instantly killed. The blast was also the loudest—heard even by British prime minister David Lloyd George at his house outside London, more than a hundred miles away. The “diameter of complete obliteration,” as an after-action report termed it, at the reluctant mine at Spanbroekmolen was 430 feet across with a crater 53 feet deep.

Throughout the war, mines had been used strictly tactically. At Messines, for the first time, military mining took on a strategic character, becoming an integral part of the overall offensive design. It was also the last time; the very nature of the conflict was changing, and mining was simply not part of that new battlefield reality in World War I. The stasis that had beset the Western Front in 1914 gave way in March 1918 to a return to maneuver warfare, with General Erich Ludendorff’s great Spring Offensive in France and Belgium. Sputtering out in July, the German drive in turn gave way to a sustained Allied push that finally brought the war to an end in November 1918.

Tens of thousands of men from Britain and the Dominions served in the BEF’s 33 tunneling companies. Many thousands were killed—often deep underground, by camouflets, cave-ins, floods, gas, and brawls with the enemy. Heroism was an everyday thing. Yet only one mole, William Hackett, was awarded the Victoria Cross—Britain’s equivalent of the United States Medal of Honor.

On June 22, 1916, Hackett was working 40 feet underground with four others. The Germans fired a large mine nearby, sealing the men in their tunnel. Teams of moles worked for two days and nights to reach them, and when they did, Sapper Hackett helped three of his comrades through the narrow hole to safety. The fourth was so seriously injured he could not be evacuated until the opening was made larger.

Hackett volunteered to stay with him, telling his rescuers, “I am a tunneler. I must look after my mate.”

Shortly afterward the roof of the mining chamber collapsed, burying both men alive. They lie there still, beneath the fields of Flanders.

This article originally appeared in the Autumn 2011 issue (Vol. 24, No. 1) of MHQ—The Quarterly Journal of Military History with the headline: “These Hideous Weapons”

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