
The elaborate network of underground tunnels where fighting continued beneath the killing fields of the Western Front during World War One has been revealed in a set of incredible images.

The photographs show the remains of tunnels where engineering soldiers, known as 'sappers' would have worked in darkness to knock out enemy German underground units.

One powerful image shows a stick grenade still stuck between two rocks as a booby trap to anyone who should try to force their way through.

Other incredible images show archived shots of troops gratefully accepting fresh air as they come above ground and fighters donning gas masks to protect against chemical warfare.

They have been released in a new book, called Beneath the Killing Fields, by Matthew Leonard for Pen & Sword Ltd.

Sappers were mainly former coal miners drafted in from the pits, but their numbers also included those who had been digging deep city sewers and the tunnels of the London Underground.

These ‘moles’ and ‘sewer rats’, as they were known, were also grimly aware that their German equivalents were doing exactly the same thing from the other direction. At any moment, they might be just a few feet away.

The Germans started the practice of tunneling, digging the first one in December 1914 just 50 miles from Calais and exploding ten smallish mines under the trenches of a British brigade.

This led to the urgent formation of British specialist tunneling companies, formed of experienced coal miners from pits all over the country. They were soon at work, sinking shafts straight down through the sandy topsoil and then as much as 80ft into the firm Flanders clay.

From the main shaft, tunnels headed off towards the enemy, in round-the-clock operations that never stopped, not even for Christmas.

Stretcher bearers of the 9th Field Ambulance, asleep on the railway embankment in front of Thames House, near Zonnebeke Railway Station in Belgium

The Wellington Mines beneath Arras were expanded by the New Zealand Tunnelling Company. By 1917 the British had learned to protect men underground before they went into battle. The Germans had started tunneling in 1914, and the British followed soon after. By mid-1916 there were 25,000 British sappers working in the continent

A view of No Man's Land near Courcelette, France during 1916. Rarely was there much to see as all life sheltered underground. A week long battle was fought here in September 1916, during the Battle of the Somme, between the French Sixth Army and the British Fourth Army and Reserve Army, against the German 1st Army

The 1st Battalion of the Newfoundland Regiment suffered more than 90 per cent casualties in just 30 minutes on the morning of 1 July 1916. The area of No Man's Land they attempted to cross has been preserved largely in tact

The main defensive positions at Beaumont Hamel. For more than two years the Germans had been constructing deep underground bunkers in the Ravine that were impervious to the British bombardment that preceeded the Battle of the Somme

This German stick grenade was found in the German T-19 tunnel system beneath Vimy Ridge. It had been wedged in a wall where Germans feared a British break-in. Sappers knew that at any point they could come face-to-face with the enemy as they tunnelled underground

Durand Group member Aidan Cleary in the Deep Deep level. The level consisted of listening tunnels, a light railway and possible tamped mine chagres. Levels of preservation were good and clear imprints of hobnail boots were recorded

The Deep Deep level contained a light railway that had remained largely in tact. This was used to transport spoil from digging as well as explosives and supplies for tunnellers. Sappers tended to have had experience working on the London Underground network, so knew what the conditions would have been like

Men of the 47th London Division advance through the British gas cloud on the morning of September 25, 1915. This was the day the Battle of Loos began, after a four-day artillery bombardment along a six-and-a-half-mile front

Leaving instructions written on the walls minimised the need to talk. Silence was paramount in front line tunnels and miners would muffle their picks and wear socks over their shoes to quieten their footsteps

Goodman contains several carvings. This face appears to be coning out of the chalk wall, a symbol of how men and landscape blended together in the subterranean world of modern warfare

During late 1917 both the French and the Germans occupied the Drachenhohle, in Austria, constructing internal walls, laying barbed wire and flooding the souterraine gas. The war continued below ground as it did above. The German word Drachenhohle mean Dragon's Cave of Mixnitz and was more than 500m long and 20m wide

The Hohenzollern redoubt seen today. This was a formidable German defensive position in 1915 consisting of machine nests, barbed wire obstacles, mantraps, supporting trenches and dug outs

Three members of the British signal service wearing gas masks in a shell hole during a gas attack. Although they may have been pleased to get fresh air when they got out of the tunnels, they soon had to don gas masks to avoid the risks of land warfare

The Lochnagar crater at La Boiselle on the Somme is as impressive as it is misleading. The Subterranean world of the Western Front was as much about attack as it was defence

WHAT IS THE LOCHNAGAR CRATER? John Norton-Griffiths, known as Hellfire Jack, was the man behind the Lochnagar crater The Lochnagar crater is a 70m deep mark of the Battle of the Somme along the Messene Ridge in Flanders. The crater is the result of an explosion which split the ground in June 1917, with the same force as an earthquake. It was the work of John Norton-Griffith, also known as “Hellfire Jack” and his group of specialist civilian miners and excavators. They had worked at coalfaces and in the Manchester sewer systems before joining the war effort. Norton was the first to raise an army of engineer soldiers to dig tunnels and lay mines under the trenches. He previously served in the Boer War. He had written to the government at the beginning of the war, to point out how useful his men could be, but his letter was not acted upon until Germany started using tunneling tactics and placed eight mines beneath the Indian Brigade in Givenchy-lès-la-Bassée. At this point Lord Kitchener called on Norton-Griffiths and the first group of men left for war. The crater was created by the detonation of a huge mine placed beneath the German front lines and its aim was to destroy a formidable strongpoint called 'Schwaben Höhe'. Close to a British trench called Lochnagar Street tunnelers dug a shaft down about 90 feet deep into the chalk. Thn, they excavated some 300 yards towards the German lines, placing 60,000 lbs (27 tons) of ammonal explosive in two large adjacent underground chambers 60 feet apart. Two minutes before the attack began, the mine was exploded, leaving the massive crater. The reason that it is so large was that the chambers were overcharged meaning sufficient explosive was used to not just break the surface and form a crater but enough to cause spoil to fall in the surrounding fields and form a lip around the crater. Debris was flung for a mile around in the explosion. The 15ft lip created protected the advancing troops from enfilade machine-gun fire from the nearby village of La Boisselle. The crater was purchased by Richard Dunning MBE on July 1 1978 and is now a memorial to all who died in the Great War. Source: Oxford Open Learning and Lochnagar Crater Advertisement

Nick Pryor and Arnaud Durier of the Durand Group in the British La Folie system beneath Vimy Ridge. A three day battle was fought here in April 1917, between four divisions of the Canadian Army and three of the German Army

A view of one of the French tunnels beneath Vauquois. Light railway tracks and extensive wooden supports were used to keep the tunnels up. There were deaths in the tunnels when mines collapsed, including two deaths underground when a German mine exploded, causing devastation overground as well, in 1916

One of the many gas doors found throughout Copse. The leather curtain has long since rotted away but the wooden frame remains in tact. This shows the way bricks have been added to the top of the frame. It was imperative that gas doors formed a perfect seal to prevent noxious gases from passing through the system