Since ancient times, armies have used mining and tunneling as a way of besieging their enemies. In classical antiquity, armies dug tunnels under enemy walls, and then set fire to timber in the tunnel, causing the shaft to collapse and with it enemy wall. Armies came up with increasingly ingenious ways to use tunnels, or to fight back against them. In 285, Sassanid Persians used poison gas to kill Roman engineers tunneling under their walls. In medieval times, gunpowder became the weapon of choice to place under enemy lines, blowing them sky-high.
The Western Front of World War I was essentially a medieval siege battle on a massive scale, and thus tunnel warfare surfaced again in history. Digging was a way of getting around the strategic impasse of trench-fighting. From the very beginning, the armies employed former miners in crude operations, digging under enemy lines, placing TNT in the mine-shafts, and then blowing up enemy trenches from below. Or tunnels could dig secret entrances into No-Man’s Land or enemy trenches, allowing soldiers to cross into enemy territory safely.
How it worked.
By 1917 tunnel warfare had become a complex and sophisticated operation. Britain recruited professional coal miners from Wales and Australia, as well as the “clay kickers” who had designed the London underground. Germany and France employed miners of their own, each side mining under enemy lines, or searching and destroying the underground tunnels of their enemies.
French sappers listen for vibrations that would detect enemy German diggers.
The most effective case ever was on June 7, 1917, when the British began the Battle of Messines by detonating 19 mines, with over 1 million tons of explosives, under German lines. The noise could be heard in London, 140 miles away. It was the loudest noise produced by humans in history up to that point, and the deadliest non-nuclear explosion of all time.
One of 19 mines goes up at Messines, June 7 1917.
Tunnel warfare was a deadly business. It came, first of all, with all the natural risks of mining. Shafts could collapse suddenly, burying sappers alive. In the clay soil of Belgium, where the water table was very high, mines flooded almost instantly, and soldiers spent laborious hours pumping out water. Complicated breathing apparatuses might be necessary for when oxygen ran out. Furthermore, sappers worked underground with massive quantities of dynamite. An accidental spark here or there and thousands of tons of TNT could blow up.
A sawn-off Lee Enfield rifle for underground fighting.
Even more risks came from the enemy. When one side mined, the other side dug counter-mines. Sappers listened for vibrations from underground, and if they heard the enemy digging, they could rig another tunnel to blow in the enemy excavation. Or, like the ancient Persians, they could find the enemy sap and siphon in gas. And sometimes the methods of war underground were truly medieval. Sometimes enemy sappers ran into each other underground, suddenly bursting through an underground wall. In these cases, nightmarish subterranean conflicts took place in the pitch dark, as man killed each other with knuckle-dusters, knives, and sawn-off bolt-action rifles.