The trench warfare of the Western Front during the First World War (1914 to 18) involved soldiers living and dying in an awful mix of mud, filth, and barbed wire. Trench systems became more sophisticated in layout as the conflict dragged on but remained rudimentary holes in the ground as entire armies attempted to shelter from artillery, gas, machine-gun, and infantry attacks. The stalemate of trench warfare was only broken in 1918 on the Western Front by the innovative use of tanks and the Allies enjoying an overwhelming numerical superiority over the enemy.

When Germany's Schlieffen plan failed to achieve a quick victory over France and that country's armed forces, with support from the British Expeditionary Force, pushed back the German advance, a situation arose where a front line was established from the Belgian coast to the Swiss border. Along this 475-mile (765-km) long Western Front, as it was called, neither side was able to make any significant advance on the enemy. Each side was obliged to better protect its armies by first digging simple holes and then, as the war dragged on, increasingly sophisticated networks of trenches and underground bunkers. Most trench systems involved digging into the mud to create three lines of trenches. There was a front trench, then a support trench, and finally a third reserve trench in the rear. Each trench was constructed in a long zigzag or with regular bends to ensure that if an enemy soldier managed to breach the defences, they could not simply fire along it unimpeded. The emphasis on irregularity also meant that at least some soldiers would be protected by a direct hit from shells. Various smaller trenches connected these three main trenches for the purposes of communication and supply. Communication between commanders and trench sections was achieved using telephones (with buried lines), runners, signal lamps, horns, and even pigeons.

There were machine gun posts situated at regular intervals, usually between the front and second trench lines, while the main artillery was positioned behind the reserve trench. German machine gun posts tended to be better built using concrete. Attacks by both sides involved a heavy artillery barrage followed by an infantry charge, but these rarely got beyond the front trench of the enemy before the machine gun posts and reserve units turned the tide. The trench systems became more sophisticated and deeper, especially on the German side and notably in the stretch known as the Hindenburg Line (from Arras to Laffaux). The Allies were under an obligation to remove German troops from French and Belgian territory and so launched more offensive operations, while the Germans were satisfied with holding on to what they had already gained. The German forces could choose the best defensive ground but also make attacks when an opportunity arose. Ultimately, the soldiers on both sides of the Western Front became stuck in a deadly game of attrition and survival that lasted four long years.

Often, the casualty figures in this war of attrition were horrendous. For example, 143,000 French soldiers died in the Champagne Offensive of December 1914, but the German trench system remained intact. Similarly, at the Battle of Loos in September-October 1915, the British, over three weeks, gained a two-mile (3.2 km) salient, but at the cost of 16,000 dead and 25,000 wounded. In battles like the Battle of the Somme and Battle of Passchendaele, the casualty figures were even higher. Not until the Allies used tanks and overwhelming numbers was this terrible static front finally broken in 1918.

The area between the two front-line trenches of each side, sometimes a distance as short as 165 feet (50 m), was known as no man's land. This area was often heavily pockmarked with shell holes and was highly dangerous since there was little or no cover. Sometimes saps, shallow trenches, or partial tunnels were built out into no man's land so that a soldier could squirm through and try and listen in on the enemy. Saps could also be used by snipers and to launch a surprise infantry attack. No man's land was bristling with reams of barbed wire to seriously slow down anyone foolish enough to try and advance, and WWI-era barbed wire contained much more barbs than standard wire used in agriculture – 16 barbs every 12 inches (30 cm), making it difficult to hold the wire anywhere when trying to cut through it. In addition, German barbed wire was especially thick, which made it extremely difficult to cut.

Although there was no standard trench design, as this depended on local geography and soil types, the trench systems on both sides shared many similarities. It is also true that the German generals, more aware that the stalemate on the battlefield might last a long time, tended to build better and more permanent structures than their British and French counterparts, who hoped trenches would be temporary if the armies could advance. Trenches were often dug by the soldiers themselves, although labourers could be used; for example, tens of thousands of Chinese labourers were used by the British. The British Army "expected 250 metres of front line trench to be dug by around 450 men in a 6 hour night-time session" (Yorke, 20). British troops even had a small digging tool issued as part of their permanent kit. In total, around 25,000 miles (40,000 km) of trenches were collectively built by all sides during the conflict.

A typical trench had sandbags and piled earth near the front edge to protect the occupants from enemy fire. The trench was deep enough for a man to stand and not be seen by the enemy, around 7 feet deep (2.1 m). A ledge was built at the base of the front wall to act as a firing step where a soldier could rise high enough to shoot over the parapet. Looking over the parapet could be fatal, and so simple periscopes were commonly used. Trenches were typically around 6 feet (1.8 m) wide at the top. Sometimes trenches had barbed wire stretched over them to impede attackers from getting in. Waterlogging and mud were a continuous problem, a situation only partially remedied by using wooden duckboards on the floor of the trench. A dugout was made into the rear wall of the trench where soldiers could eat and sleep. Walls were shored up using wood or corrugated iron. Later German shelters could be as deep as 32 feet (10 m) and virtually bombproof. Latrines, simple earth pits, were usually located in a short cut-out passage to the rear of a trench. There were no washing facilities for ordinary soldiers, and they were expected to shave from dirty water in their helmets.

Weather and artillery hits meant trenches had to be constantly repaired. As sections of trenches were constantly being abandoned because of flooding, artillery damage, or loss to the enemy, and new sections were built as a defensive improvement or as new territory was gained, the whole trench system became a maze that soldiers often got lost in. Certainly, troops newly arrived at the front required guides to show them which trenches led where. Similarly, a system of signs was implemented to help soldiers find their way. As trench systems constantly evolved, commanders were ever-anxious to know the enemy's positions, and so there were frequent night patrols across no man's land to supplement information gathered from reconnaissance flights and spotters in balloons.

Life in the trenches could be tedious indeed, with nothing to do except read, write letters, or play cards for long periods. Rations in the trenches were meagre and unpalatable, the typical fare being hard bread or biscuits, and unspeakable stews whose true contents caused much speculation. Rare treats included jam, bacon, cheese, and rum. British troops were relieved from front trench duty every four days. Soldiers typically spent the next four days in the support trench and then the next eight in the reserve trench. After a period of around eight days in a rest camp, a soldier was sent back to a front trench. In some French and German units, periods spent at the front line were much longer or even semi-permanent. No matter which trench a soldier found himself in, lice followed him. Rats were another disagreeable part of life in the trenches. Diseases spread rapidly amongst the men, and a common ailment was 'trench foot', a swelling of the feet caused by constant exposure to water. Then there were the hazards of fighting, of course: phosgene or chlorine gas attacks, mortar fire, sniper fire, hand grenades, a charging enemy armed with rifle, bayonet, or flame-thrower, aerial attacks later in the war, and most persistent of all, heavy shelling, which, even if one survived, often left its mark in the form of shell shock, then a little understood reaction to constant explosions. Life in the trenches was to be endured, and, with only a 50 to 50 chance of escaping death or injury, the idea of survival and finally returning home was a fragile hope few managed to keep intact through this terrible war.

On the German side, Ernst Jünger gives the following description of his trench system:

To reach the front line, the firing trench, we take one of the many 'saps', or communication trenches, whose job it is to afford the troops some protection on their way to battle stations. These, often very long, trenches are broadly perpendicular to the front, but, to make it less easy to rake them with fire, they most often follow a zigzag or curving course. After a quarter of an hour's march, we enter the second trench, the support trench, which is parallel to the firing trench, and serves as a further line of defence should that be taken.

The firing trench…is dug to a depth of ten or twenty feet. The defenders move around on the bottom of a mine gallery; to observe the ground in front of the position, or to fire out, they climb a set of steps or a wide wooden ladder to the sentry platform, which is set at such a height in the earth that a man standing on it is a head taller than the top of the rampart. The marksman stands at his sentry post, a more or less armoured niche, with his head protected by a wall of sandbags or a steel plate. The actual lookout is through tiny slits through which a rifle barrel is pushed….Rank weeds climb up and through the barbed wire, symptomatic of a new and different type of flora taking root on the fallow fields…

To rest in, there are dugouts, which have evolved by now from rudimentary holes in the ground to proper enclosed living quarters, with beamed ceilings and plank-cladded walls. The dugouts are about six feet high, and at a depth where there floors are roughly level with the bottom of the trench outside. In effect, there is a layer of earth on top of them thick enough to enable them to survive oblique hits. In heavy fire, though, they are death-traps…

The whole thing should be pictured as a huge, ostensibly inert installation, a secret hive of industry and watchfulness, where, within a few seconds of an alarm being sounded, every man is at his post. But one shouldn't have too romantic an idea of the atmosphere, there is a certain prevailing torpor that proximity to the earth seems to engender.

(40 to 41)

Life in the trenches could be surprisingly quiet until the illusion of peace was shattered by a terrible flurry of activity, as here described by British soldier Private Harry Saunders:

It was one of those nights when the guns on both sides were quiet and there was nothing to show there was a war on. The attack began with flares. After this, a line of hissing cylinders sent a dense grey mist rolling over no man's land. What breeze there was must have been exactly right for the purpose, and that creeping cloud of death and torment made a nightmare scene I shall never forget. It seemed ages before the Germans realised what was happening. At last, however, the first gas alarm went and I think most of us were glad to think they would not be taken unawares. I was haunted for hours afterwards by the thought of what was happening over there.

(Williams, 33).

In such terrible conditions and living in such close proximity, special bonds were forged between the men, bonds all too often broken by the frequency of death and injury. Ernst Jünger describes the monotony of casualties sustained in the trenches:

We observe the front line opposite through binoculars or periscopes, and often manage to get in a head shot or two through a sniper's rifle. But careful, because the British also have sharp eyes and useful binoculars.

A sentry collapses, streaming blood. Shot in the head. His comrades rip the bandage roll out of his tunic and get him bandaged up. 'There's no point, Bill.' 'Come on, he's still breathing, isn't he?' Then the stretcher-bearers come along, to carry him to the dressing-station. The stretcher poles collide with the corners of the fire-bays. No sooner has the man disappeared than everything is back to the way it was before. Someone spreads a few shovelfuls of earth over the red puddle, and everyone goes back to whatever he was doing before. Only a new recruit maybe leans against the revetment, looking a little green about the gills.

(47)

Although death was a numbing part of each and every day, memories of those lost lingered. Siegfried Sassoon (1886 to 1967), the poet who served in the trenches, writes in this passage from A Working Party:

A flare went up; the shining whiteness spread
And flickered upward, showing nimble rats
And mounds of glimmering sand-bags, bleached with rain;
Then the slow silver moment died in the dark.
The wind came posting by with chilly gusts
And buffeting at corners, piping thin.
And dreary through the crannies; rifle-shots
Would split and crack and sing along the night,
And shells came calmly through the drizzling air
To burst with hollow bang below the hill.
Three hours ago he stumbled up the trench;
Now he will never walk that road again:
He must be carried back, a jolting lump
Beyond all needs of tenderness and care.

He was a young man with a meagre wife
And two small children in a Midland town;
He showed their photographs to all his mates,
And they considered him a decent chap
Who did his work and hadn't much to say,
And always laughed at other people's jokes
Because he hadn't any of his own.

(Kendall, 89 to 90)