Lochnagar Crater 1 July 1916: Complete Field Guide — Tunnellers, the Mine & La Boisselle

At 7:28am on 1 July 1916, the ground south of La Boisselle opened.

Two minutes before the British infantry assault began on the first day of the Somme, 179th Tunnelling Company Royal Engineers fired the Lochnagar mine beneath the German position. Sixty thousand pounds of ammonal erupted under the front line. Earth and chalk were thrown high into the air. A crater roughly 100 metres across and 21 metres deep was left behind.

The explosion is one of the most famous images in the story of the Somme. The harder history begins immediately afterwards: what the mine was meant to do, what it actually achieved, what happened to the infantry advancing around it and why this scar in the ground survived when most similar craters disappeared.

At a glance

• Location: south of La Boisselle, Somme, France.
• Date detonated: 1 July 1916.
• Time: 7:28am.
• Unit: 179th Tunnelling Company, Royal Engineers.
• Explosive: approximately 60,000lb of ammonal in two charges.
• Tunnel length: approximately 1,030ft / 314m.
• Crater: about 330ft / 100m across and 70ft / 21m deep.
• Infantry sector: 34th Division.
• Battle: opening of the Battle of the Somme.

Why there were mines under the Somme

Static trench warfare produced a second battlefield underground.

Both sides dug beneath No Man’s Land to place explosives under enemy positions or to intercept enemy miners. The work was slow, claustrophobic and extraordinarily dangerous. Sound mattered as much as sight. A scrape in chalk could reveal a gallery. A charge fired underground could kill men without anyone above seeing the fight.

By 1916 British tunnelling companies had become specialised formations of the Royal Engineers, combining mining skill, engineering and listening technology.

La Boisselle before 1 July

The ground around La Boisselle had already been heavily mined. The village and its approaches sat on a strong part of the German front, and the underground war had produced craters and counter-mines before the Somme offensive began.

The Lochnagar Crater Foundation records a particularly lethal German camouflet on 4 February 1916 that killed eighteen men during underground work in the sector, including officers involved in geophone experiments.

The July mine therefore did not emerge from a clean engineering project. It came after months of underground contest.

179th Tunnelling Company

179th Tunnelling Company began driving the Lochnagar gallery in November 1915.

The final tunnel extended roughly 1,030 feet through the chalk. As it approached the German line, silence became critical. The Foundation’s history describes miners working with bayonets fitted with handles rather than ordinary picks, standing on sandbags and passing chalk spoil back quietly.

Every metre nearer the enemy increased the risk that German listeners would detect the work.

How you hide a tunnel

Tunnelling under an enemy position was not simply a digging problem.

Air had to move. Spoil had to disappear. Timbering had to support the gallery. Men and explosives had to move through narrow spaces without producing enough noise to reveal the operation.

Listening posts and geophones helped detect enemy work. Counter-miners could detonate a smaller underground charge — a camouflet — designed to crush an enemy gallery before it reached the target.

The underground battle was therefore a contest of patience and sound.

The charges

The Lochnagar mine used two explosive chambers around 60 feet apart. Together they contained approximately 60,000lb of ammonal.

That figure is the one used by the Lochnagar Crater Foundation. Older captions and popular accounts sometimes give a lower tonnage, which is one reason figures for the mine vary between retellings.

The charges were deliberately large enough not only to rupture the German position but to throw substantial spoil outward, creating a raised lip that might provide some protection from flanking fire.

Why 7:28am?

The British infantry attack was scheduled for 7:30am.

Lochnagar and the neighbouring Y Sap mine were fired at 7:28 — two minutes beforehand.

The intention was to destroy or disrupt the German position, shock survivors and create terrain that could help the assaulting troops. The short interval was also meant to prevent German troops recovering fully before the infantry arrived.

Two minutes sounds short. Under fire, across broken ground, it can be a long time.

The explosion

The Lochnagar Foundation gives the resulting crater as roughly 330 feet across and 70 feet deep, with a lip around 15 feet high.

Royal Flying Corps pilot Cecil Lewis witnessed the eruption from the air and later described an enormous column of earth rising thousands of feet.

From ground level the effect was different: blast, falling debris, altered terrain and a new obstacle that immediately had to be incorporated into an infantry battle.

A mine does not make the enemy disappear

One of the dangerous myths about First World War mining is that a giant explosion simply removed the defensive problem.

The mine destroyed part of the German position. It did not destroy every machine-gun post, trench, dugout or supporting position around La Boisselle.

German troops outside the immediate blast area could recover. Nearby defences could fire across the crater. British infantry still had to cross open ground and clear surviving positions.

34th Division

The sector around Lochnagar was attacked by 34th Division, including battalions from the Tyneside Scottish and Tyneside Irish brigades as well as other units.

The Foundation records 6,380 officers and men of the division killed, wounded or missing on 1 July — the heaviest divisional casualty total of the day.

That figure covers the division’s fighting across its whole attack, not men killed at the crater itself. It should not be presented as “Lochnagar casualties”.

The lip as cover — and obstacle

The crater lip could provide protection from some lines of fire, which was part of the reason for overcharging the mine.

But a crater that size also breaks movement. Infantry arriving at it has to decide whether to enter, skirt, occupy or pass around it. Units can become channelled. Commanders lose sight of men behind the rim. Casualties and stragglers collect in dead ground.

An engineered feature intended to help an assault immediately becomes terrain that both sides can exploit.

Did the Lochnagar mine succeed?

It depends on the question.

Did it detonate as planned? Yes.

Did it destroy a section of the German position? Yes.

Did it produce the intended massive crater and protective lip? Yes.

Did it unlock La Boisselle or make the divisional attack straightforward? No.

The official-history judgement quoted by the Lochnagar Foundation was that the mines fired on 1 July were too dispersed along the front to create a decisive general effect.

That is a better assessment than either extreme: the mine was not pointless, but nor was a spectacular explosion equivalent to a tactical breakthrough.

The crater during the battle

After the opening assault, the crater became part of the battlefield rather than a one-moment spectacle.

Troops used the lip and interior for cover. The area remained dangerous and contested. Later photographs show British troops moving around the crater months after the opening day.

As the front moved east, its tactical importance faded.

Burials and the post-battle landscape

The crater was used for shelter and temporary burial during the war.

That matters when visiting it today. The site is not only the remnant of an engineering operation. It sits within ground where men fought, died and were temporarily buried.

The landscape itself became a record before anyone decided to preserve it as a memorial.

Why Lochnagar survived

Many First World War mine craters were later filled, farmed over or absorbed into the landscape.

Lochnagar remained.

In 1978 Richard Dunning purchased the crater to prevent it being filled in. Volunteer work gradually transformed the site into a preserved battlefield landmark and place of remembrance.

That preservation decision is why visitors can still stand on the lip rather than read about the crater from a sign beside a flat field.

Lochnagar today

The Lochnagar Crater Foundation describes the site around three ideas: conservation, commemoration and reconciliation.

The crater is privately owned but preserved for public remembrance. Annual ceremonies are held on 1 July.

The modern purpose is deliberately wider than celebrating British military engineering. The site remembers people of all nations affected by war.

1 July ceremony

The current ceremony includes a lone piper, wreath laying, readings, the Exhortation, the Last Post, two minutes’ silence and Reveille.

Poppy and cornflower petals are scattered into the crater, and participants link hands around the rim as a symbol of reconciliation.

That ceremony turns a feature created to destroy an enemy position into a place used to bring former enemies into the same act of remembrance.

The view from the rim

Lochnagar is one of those battlefield sites where scale makes sense only when you stand beside it.

From the rim, the relationship between the crater, La Boisselle and the surrounding ground becomes clearer. The lip blocks sight. The open fields make the infantry problem visible. Nearby ridges and villages explain why one destroyed position could not solve the wider attack.

This is exactly why terrain belongs in military history.

Lochnagar and the Somme

The crater should never become a substitute for the whole first day of the Somme.

It is one engineered point on a front many miles long. The British Army detonated multiple mines that morning. Different divisions faced different terrain, wire, artillery effects and German positions.

What Lochnagar gives us is a close-up: months of underground preparation condensed into one explosion, followed by the same infantry reality everyone else faced.

Visit with the right question

Do not stand at the crater and ask only, “How big was the explosion?”

Ask where the German line ran. Where did 34th Division have to go next? What could still fire into the sector? How did men find direction after the ground itself had been rearranged?

The crater is spectacular. The battle around it is the history.

Related Field Notes

• Battle of the Somme 1916 — Complete Field Guide
• First World War 1914–1918 — Western Front Campaign Guide
• British Remembrance — Complete Field Guide

Wear the history

Lochnagar Crater 1 July 1916 T-Shirt — Battle of the Somme →

Sources & further research

• Lochnagar Crater Foundation — History.
• Lochnagar Crater Foundation — Mining at Lochnagar.
• Lochnagar Crater Foundation — Statistics.
• Lochnagar Labyrinth — tunnelling and 34th Division.
• Lochnagar Crater Foundation — 1 July Remembrance Ceremony.