Stretching hundreds of miles across the Western Front, millions of soldiers fought in trenches during World War I — with horrific physical and mental consequences.
Trench warfare effectively defined World War I. Though this military tactic can be traced back centuries, the large-scale use of trenches in World War I resulted in some of history’s most hellish battles.
Historically, trenches had been used as a defense strategy against invaders — think of a moat surrounding a castle — but the advent of modern weaponry during World War I meant that trenches now needed to protect soldiers against machine-gun fire and artillery attacks. Troops on both sides of the conflict dug these long, narrow ditches and occupied them for weeks at a time while facing an onslaught of bullets, gas, and mortar shells.
Indeed, life inside the trenches was brutal. Gas attacks and flamethrowers often led to painful, agonizing deaths for soldiers, whose bodies were left to pile up in the trenches-turned-graves that they had helped build.
See some of the most horrific images of World War I trenches in the gallery below, then learn more about the history behind this catastrophic warfare.
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Soldiers in the reserve trenches in Beaumont Hamel, France, during World War I. The Print Collector/Getty Images
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French soldiers raid a German trench during World War I. Bettmann/Getty Images
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The front line around Aisne, France. 1914.The Print Collector/Print Collector/Getty Images
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An American nurse wearing a gas mask while working in the trenches. Russell/Getty Images
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An American soldier sitting in a small nook, writing a letter to home. Bettmann/Getty Images
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Dead German soldiers lying in a trench after the Battle of Cambrai. November 23, 1917.Hulton Archive/Getty Images
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Dead British and German soldiers near the Hohenzollern Redoubt, a fortified position on the German lines that was the site of brutal fighting during the Battle of Loos.The Print Collector/Print Collector/Getty Images
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British soldiers lined up in a narrow trench. October 28, 1914.Hulton Archive/Getty Images
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British soldiers making grenades from tins in the trenches. Circa 1915. Hulton Archive/Getty Images
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A French trench before an attack during the Second Battle of Champagne. September 25, 1915. The Print Collector/Getty Images
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Seven French soldiers having lunch at a makeshift table inside the trenches. 1917.Galerie Bilderwelt/Getty Images
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A tank over a trench during the Battle of Cambrai. Photo 12/Universal Images Group via Getty Images
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Soldiers transporting their wounded comrade to a first aid post in Passchendaele, Belgium.The Print Collector/Getty Images
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A combat demonstration in a German trench. 1915. ullstein bild/ullstein bild via Getty Images
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An American soldier in a trench. Circa 1918.FPG/Hulton Archive/Getty Images
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During the Second Battle of Ypres, German troops released 168 tons of chlorine gas over a four-mile front, surprising French and Algerian soldiers with the first gas attack of World War I. April 22, 1915.The Print Collector/Print Collector/Getty Images
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French soldiers and a dog wearing gas masks in a trench. Circa 1916.Culture Club/Getty Images
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Soldiers often occupied trenches for weeks at a time during World War I, putting them at risk for many attacks as well as disease.Print Collector/Getty Images
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A flamethrower attack during the German Spring Offensive.ullstein bild/ullstein bild via Getty Images
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The body of a dead German soldier lies in a trench. 1918.The Print Collector/Print Collector/Getty Images
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Men of the Lancashire Fusiliers on the Western Front. Circa 1917.Lt. J W Brooke/Imperial War Museums via Getty Images
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German soldiers of the 12th Regiment playing cards in a dugout in a trench in German-occupied Russian Poland during World War I. PA Images via Getty Images
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French soldiers lining the trenches in Calonne. 1915.The Print Collector/Getty Images
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Soldiers digging trenches in Arras, France.Pen & Sword/SSPL/Getty Images
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German soldiers sleeping in a trench while two others stand guard near the Aisne River valley on the Western Front. 1914.Hulton Archive/Getty Images
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A captured German soldier being interrogated.The Print Collector/Getty Images
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Soldiers picking lice from their clothing inside a trench. 1915.Bettmann/Getty Images
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Russian infantry soldiers in shallow trenches during a battle against the Austro-Hungarian army on the Eastern Front of World War I.Daily Mirror/Mirrorpix/Mirrorpix via Getty Images
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A medical auxiliary tending to wounded soldiers in a trench. 1916.Topical Press Agency/Getty Images
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English soldiers in French trenches charging forward during an assault. 1916.Fototeca Gilardi/Getty Images
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Trench warfare on the Hindenburg Line, a vast system of defenses built by German troops on the Western Front in the winter of 1916-1917. The Print Collector/Print Collector/Getty Images
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Mortars in the trenches. The Print Collector/Print Collector/Getty Images
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A dead British soldier lies at the bottom of a trench, near St. Quentin, France. Circa 1917. Henry Guttmann Collection/Hulton Archive/Getty Images
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A group of soldiers resting in a shallow, hastily dug trench. Public Domain
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The Russian Offensive during World War I. The Print Collector/Print Collector/Getty Images
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French soldiers targeting German trenches with gas and flame attacks in Flanders, Belgium. 1918.DOD, Signal Office/Buyenlarge/Getty Images
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Dead soldiers in a captured German trench. 1916.Robert Hunt/Windmill Books/Universal Images Group via Getty Images
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Belgian soldiers in trenches along a railway that they guarded against the Germans during the Battle of Hofstado. George Rinhart/Corbis via Getty Images
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Women assigned to work the trenches. Museo Centrale del Risorgimento/Mondadori via Getty Images
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Soldiers in the trenches along the Belgian front. Roger Viollet via Getty Images
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A nurse applying first aid to a soldier in a French trench. Circa 1915.The Print Collector/Getty Images
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A French soldier standing near the bodies of dead German troops after successfully taking over the German trench. Roger Viollet via Getty Images
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A group of Portuguese soldiers entering a "gas trench" as part of their training for gas warfare during World War I. Public Domain
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An Indian infantry digging trenches in France. Public Domain
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Troops transporting a wounded soldier through the narrow trench system. Public Domain
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A soldier frying bacon over a small fire inside a trench. Public Domain
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A section of Seaforth Highlanders taking a brief respite in a trench. The Print Collector/Getty Images
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Scottish soldier "Piper" Daniel Laidlaw playing on the parapet of the German trenches.George Rinhart/Corbis via Getty Images
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The remains of a British soldier found weeks after a battle. All that remained were the skeleton, his helmet, and his weapons.SeM/Universal Images Group via Getty Images
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Two soldiers wearing gas masks in a trench.Public Domain
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A fatigue party carrying duckboards out of a support line trench at night in Cambrai. 1917.Lt. J W Brooke/Imperial War Museums via Getty Images
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Fighting continues as one wounded soldier is tended to inside a trench. Public Domain
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A Cheshire Regiment trench in Somme. 1916.Public Domain
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Dressing a wounded soldier's injuries. Public Domain
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Dead Turkish soldiers who were left behind after a British circling movement forced the defending battalion to abandon their trenches on the heights defending Bosporus.Bettmann/Getty Images
How World War I Trenches Became A Cesspool Of Disease And Devastation
When fighting first began on the Western Front — a region of northern France and Belgium that primarily saw fighting between Allied troops and Germans — it started as a steady forward movement. However, with little protection in the open fields, soldiers on both sides were forced to begin digging trenches as a way to shield themselves from machine-gun fire.
Gradually, the fighting slowed, with both sides now occupying trenches for weeks, establishing not just defensive measures but also makeshift shelters within them. The trenches afforded troops extra time to prepare their defensive measures, but they also came with their own share of problems.
According to The National WWI Museum and Memorial, any protection provided by the trenches was often countered by the unsanitary, tightly-packed conditions inside. Despite troops laying down wooden duckboards and sandbags to prevent water from flowing into the trenches, water still found its way in, meaning soldiers were often covered in damp mud.
"The mud in Belgium varies in consistency from water to about the thickness of dough ready for the oven," wrote one British soldier.
Robert Hunt/Windmill Books/Universal Images Group via Getty ImagesA shell bursting near German troops manning a trench along the Western Front.
The constant dampness led to a condition known as "trench foot," which caused dead tissue to spread across the foot and could require amputation if left untreated — otherwise, the afflicted soldier could die of infection.
Then, there was the spread of disease and other illnesses like dysentery, typhoid fever, and a condition known as "trench mouth," a type of gum infection. The filthy state of makeshift kitchens and overflowing toilets in the trenches only hastened the spread of illness among the troops.
Trenches took a mental toll on many soldiers as well. Because troops were living under the threat of bombardment, and fighting in such close proximity, many World War I veterans suffered from "shell shock," an outdated term for what is now known as post-traumatic stress disorder (PTSD).
And while disease had been common during past wars — often killing more soldiers than combat — World War I also marked the first conflict in history to have more deaths caused by combat than any other factor.
Why Trench Warfare Led To So Many Casualties
During World War I, the term "no man's land" referred to the area between established strategic fronts for opposing armies. This region, which belonged to no one side in particular, is where much of the actual fighting took place.
Unsurprisingly, no man's land was a hellish, desolate landscape.
The land was riddled with shrapnel, shells, tree stumps, and barbed wire. Early on in the war, soldiers initially employed a strategy of mounting attacks from the trenches, climbing up over the tops of the trenches and charging forward into no man's land against an onslaught of bullets and gas.
According to HISTORY, this strategy proved ineffective, and so forces later began mounting surprise attacks from the trenches at night.
Universal History Archive/UIG via Getty ImagesA German Mark IV tank known as "Hyacinth" stuck in a trench.
The Germans were especially successful at this, regularly attacking opposing forces' trenches at weak points in the dark. Sometimes, German soldiers also circled around to attack their enemy troops at the rear.
Most infamously, the brutality of trench warfare resulted in one of the deadliest battles of World War I, the Battle of the Somme in France, where 60,000 British soldiers suffered casualties on just the first day of fighting.
But even early on, it was clear that this was a war unlike any the world had seen before. And the trenches often hurt more than they helped.
Though the ditches offered troops some protection from bullets, the narrow passageways and grisly conditions of the trenches often added to the suffering of soldiers who were already wounded or ill. These defensive shelters became garbage dumps and mass graves as the war raged on, and sometimes even traps as artillery fire rained down or deadly gas spread.
In the end, the total number of military and civilian casualties in World War I exceeded 40 million, with more than 20 million dead and 20 million wounded. And many soldiers met their ends in the trenches.
A staff writer for All That's Interesting, Austin Harvey has also had work published with Discover Magazine, Giddy, and Lucid covering topics on mental health, sexual health, history, and sociology. He holds a bachelor's degree in screenwriting (widely considered to be a bad move) from Point Park University.