See L. Wolff, In Flanders Fields: the 1917 Campaign (1958).
Trenches did impede an attacking enemy's movement and provided a psychological benefit for the men manning them. With this in mind, it became common practice for Roman legions to entrench their encampments every night. A fortified camp was extremely hard to assault directly, and a Roman commander who did not wish to engage an enemy could often simply remain encamped.
Once siege engines (such as the trebuchet) were developed, the techniques involved in assaulting a town or a fortress became well known and ritualised—the siège en forme. The attacking army would surround a town. Then the town would be asked to surrender. If it did not comply, the besieging army would invest (surround) the town with temporary fortifications to stop sallies from the stronghold or relief getting in. The attackers would then build a length of trenches parallel to the defences and just out of range of defending artillery. They would then dig a trench towards the town in a zigzag pattern so that it could not be enfiladed by defending fire; it also created a good vantage point from which to survey the enemy. Once within artillery range another parallel trench would be dug with gun emplacements. If necessary using the first artillery fire for cover, this process would be repeated until the guns were close enough to be laid accurately to make a breach in the fortifications. In order that the "forlorn hope" and their support troops could get close enough to exploit the breach, more zigzag trenches could be dug even closer to the walls with more parallel trenches to protect and conceal the attacking troops.
In 1849 (a decade before the American Civil War) George Ripley wrote:
The first development that was essential for modern trench warfare however was the introduction of mass-conscripted armies during the French Revolution and the Napoleonic Wars. Prior to this, armies still consisted of small numbers of troops, which were unable to defend a large territory for very long—battles were either brief or degenerated into siege warfare. Large armies made it much more difficult for one army to outflank another, but it was still possible with cavalry and infantry charges for one army to break another by a direct assault. An example of early fortified military lines that stretched for many miles were the Lines of Torres Vedras (1810), built by the Portuguese under the direction of Royal Engineers of the British Army during the Peninsular war.
Trench warfare was not limited to Europe, either. The Māori of New Zealand had built stockades called Pā on hills and small peninsulas for centuries before European contact, independent of outside knowledge. These resembled the small Iron Age forts which dot the British and Irish landscapes. When the Māori encountered the British they developed the Pā into a very effective defensive system of trenches, rifle pits and dugouts, which predated similar developments in America and Europe. In the New Zealand land wars for a long time the modern Pā effectively neutralised the overwhelming disparity in numbers and armaments. At Ohaeawai Pā in 1845, at Rangiriri in 1864, and again at Gate Pā in 1864 the British and Colonial Forces discovered that a frontal attack on a defended Pā was both ineffective and extremely costly.
Frontal assault became increasingly suicidal due to the development of improved firearm technology in the mid-19th century. When the American Civil War began in 1861, it was fought with Napoleonic tactics. By 1863, it had many of the characteristics of the First World War, including trenches, rifles, rapid-fire weapons (in WW1, machine guns), field fortifications, and massive casualties. The Battle of Petersburg, near the end of the war, with its trenches and static formations, contrasts sharply with the early battles, such as the First Battle of Bull Run, where manoeuvre was still possible; famous charges, such as George Pickett's at the Battle of Gettysburg, revealed the futility of direct assault on an entrenched opposing line.
Several factors were responsible for the change. First, there was the proliferation of rifles (such as the .58 (14.7mm) Springfield), manufactured in the thousands. Effective at double the range of the typical smoothbore of the Napoleonic era (and able to kill a man at over 1000 m), they enabled men sheltering in a trench or behind an improvised obstacle to hold a body of attackers at a much greater distance than before; attackers were unable to cross the swept zone rapidly enough to avoid prohibitive casualties. Rifles had been used with considerable success in the American Revolution and War of 1812, but were slow to reload and were often personal hunting weapons of frontiersmen. By the 1850s, the Minié ball allowed rifles, already widely adopted, to become very much more lethal. Second was the persistence of essentially Napoleonic columnar tactics, which magnified losses; only late in the war did open order (or skirmish line) become standard. Thus, the first response to increased firepower (taking cover) and the second (dispersal of troops) were eventually adopted. The third (armour) was not then an option, as it had been in the face of Welsh or Mongol bows; the fourth, speed (crossing the swept zone faster), was not either, for the fastest battlefield transport was the horse, and cavalry proved as vulnerable as infantry to the new weapons. This would persist into World War One.
Other factors appearing after the end of the American Civil War played a part. The first was the development of barbed wire (invented in 1874), which in itself did only minor harm, but, crucially, could slow the progress of an attacking force and thus enable emplaced gunners to inflict crippling losses. A second was the improvement of artillery. Artillery in one form or another had been a part of warfare since classical times, and from the rise of gunpowder until the development of trench warfare in the 1860s had been the major killing force; it was supplanted only temporarily by the rifle. With the development of steel breechloading guns by Krupp, however, much of its former power was restored (as graphically demonstrated in the Franco-Prussian War of 1870–71). Third was the introduction of high explosive shells, which amplified killing power up to sixteenfold. Fourth, hydraulic recoil mechanisms, pioneered by the French 75 mm M1897 (the famed "French 75") significantly increased the rate of fire and accuracy. These magnified the effectiveness of artillery to a degree unimaginable in the 1870s. The swept zone between attacker and defender became a "no man's land", too lethal to cross. The introduction of telephone communication permitted artillery spotting far from the physical artillery batteries -- widening artillery usefulness in indirect fire and speeding shifting of targets.
Although firearms technology and the conscript army dramatically changed the nature of warfare, most armies were completely unaware of the implications of these changes and were not prepared for their consequences. As early as 1864, the opposing armies in the American Civil War were entrenched near Petersburg, Virginia for months, and tactics which were later to be tried in Europe, such as subterranean mines, were employed to break the stalemate -- to little effect.
At the start of World War I, most armies prepared for a brief war whose strategy and tactics would have been familiar to Napoleon. Indeed, a number of horse cavalry units were brought to the front by train, commanded by officers who did not imagine the factors that would render them useless. Most of these units were never deployed. Infantry, armed with bolt action rifles and augmented by machine guns, needed only to dig in a bit to become nigh invulnerable. To attack frontally was to court crippling losses, so an outflanking operation was essential. After the Battle of the Aisne in September 1914, an extended series of attempted flanking moves, and matching extensions to the fortified defensive lines, soon saw the celebrated "race to the sea"; German and Allied armies produced essentially a matched pair of trench lines from the Swiss border in the south to the North Sea coast of Belgium. Trench warfare prevailed on the Western Front from September 16, 1914, until the Germans launched their "Spring Offensive", Operation Michael, on March 21, 1918.
On the Western Front, the small improvised trenches of the first few months rapidly grew deeper and more complex, gradually becoming vast areas of interlocking defensive works. Such defensive works resisted both artillery barrages and mass infantry assaults. The space between the opposing trenches was referred to as "no man's land" (for its lethal uncrossability) and varied in width depending on the battlefield. On the Western Front it was typically between 100 and 300 yards (90-275 m), though only 30 yards (27 m) on Vimy Ridge. After the German withdrawal to the Hindenburg line in March 1917, it stretched to over a kilometre in places. At the infamous "Quinn's Post" in the cramped confines of the Anzac battlefield at Gallipoli, the opposing trenches were only 15 m (16yd) apart and an incessant bombing war was waged there. On the Eastern Front and in the Middle East, the areas to be covered were so vast, and the distances from the factories supplying shells, bullets, concrete and barbed wire so great, trench warfare in the European style often did not eventuate.
In the Alps, trench warfare even stretched onto vertical slopes and deep into the mountains, to heights of 3900 m (12795 ft) above sea level (the Ortler had an artillery position on its summit near the front line). The trench-line management and trench profiles had to be adapted to the rough terrain, the hard rock, and the harsh weather conditions. Many trench systems were constructed within glaciers like the Adamello-Presanella group or the famous city below the ice on the Marmolada in the Dolomites.
Very early in the war, British defensive doctrine suggested a main trench system of three parallel lines, interconnected by communications trenches. The point at which a communications trench intersected the front trench was of critical importance, and it was usually heavily fortified. The front trench was lightly garrisoned and typically only occupied in force during "stand to" at dawn and dusk. Between 70 and 100 yards (64-91 m) behind the front trench was located the support (or "travel") trench, to which the garrison would retreat when the front trench was bombarded. Between 300 and 500 yards (275-460 m) further to the rear was located the third reserve trench, where the reserve troops could amass for a counter-attack if the front trenches were captured. This defensive layout was soon rendered obsolete as the power of the artillery grew; however, in certain sectors of the front, the support trench was maintained as a decoy to attract the enemy bombardment away from the front and reserve lines. Fires were lit in the support line to make it appear inhabited and any damage done immediately repaired.
Temporary trenches were also built. When a major attack was planned, assembly trenches would be dug near the front trench. These were used to provide a sheltered place for the waves of attacking troops who would follow the first waves leaving from the front trench. "Saps" were temporary, unmanned, often dead-end utility trenches dug out into no-man's land. They fulfilled a variety of purposes, such as connecting the front trench to a listening post close to the enemy wire or providing an advance "jumping-off" line for a surprise attack. When one side's front line bulged towards the opposition, a "salient" was formed. The concave trench line facing the salient was called a "re-entrant." Large salients were perilous for their occupants because they could be assailed from three sides.
Behind the front system of trenches there were usually at least two more partially prepared trench systems, kilometres to the rear, ready to be occupied in the event of a retreat. The Germans often prepared multiple redundant trench systems; in 1916 their Somme front featured two complete trench systems, one kilometer apart, with a third partially completed system a further kilometer behind. This duplication made a decisive breakthrough virtually impossible. In the event that a section of the first trench system was captured, a "switch" trench would be dug to connect the second trench system to the still-held section of the first. The Germans made something of a science out of designing and constructing defensive works. They used reinforced concrete to construct deep, shell-proof, ventilated dugouts, as well as strategic strongpoints. They were more willing than their opponents to make a strategic withdrawal to a superior prepared defensive position. They were also the first to apply the concept of "defense in depth," where the front-line zone was hundreds of yards deep and contained a series of redoubts rather than a continuous trench. Each redoubt could provide supporting fire to its neighbours, and while the attackers had freedom of movement between the redoubts, they would be subjected to withering enfilade fire. The British eventually adopted a similar approach, but it was incompletely implemented when the Germans launched the 1918 "Spring Offensive" and proved disastrously ineffective. France, by contrast, relied on artillery and reserves, not entrenchment. The characteristic barbed wire placed before trenches, in belts 15 m (50 ft) deep or more, differed, too; the German wire was heavier gauge, and British wire cutters (designed for the thinner native product) were unable to cut it.
Trenches were never straight but were dug in a zigzagging pattern that broke the line into bays connected by traverses. This meant that a soldier could never see more than 10 metres (30 ft) or so along the trench. The trenches were dug like this so an enemy would not be able to attack from the sides thus causing major damage. Consequently, the entire trench could not be enfiladed if the enemy gained access at one point; or if a bomb or shell landed in the trench, the fragmentation (often called shrapnel) could not travel far. Another bonus for building trenches in a zig zag pattern was that if enemy aircraft were sent to gather intelligence for artillery strikes, it would be harder for them to accurately give co-ordinates for zig zagging trenches than straight trenches. The side of the trench facing the enemy was called the parapet and had a fire step. The rear of the trench was called the parados. The parados protected the soldier's back from fragmentation from shells falling behind the trench. If the enemy captured the trench, then the parados would become their "parapet". The sides of the trench were revetted with sandbags, wooden frames and wire mesh. The floor of the trench was usually covered by wooden duckboards.
Dugouts of varying degrees of luxury would be built in the rear of the support trench. British dugouts were usually 8 to 16 feet (2.5-5 m) deep, whereas German dugouts were typically much deeper, usually a minimum of 12 feet (3.6 m) deep and sometimes dug three stories down, with concrete staircases to reach the upper levels. "Luxury" was a relative term when prolonged rain reduced the floor and walls to mud.
To allow a soldier to see out of the trench without exposing his head, a loophole would be built into the parapet. A loophole might simply be a gap in the sandbags, or it might be fitted with a steel plate. German snipers used armour-piercing bullets that allowed them to penetrate loopholes. The other means to see over the parapet was the trench periscope—in its simplest form, just a stick with two angled pieces of mirror at the top and bottom. In the Anzac trenches at Gallipoli, where the Turks held the high ground, the periscope rifle was developed to enable the Australians and New Zealanders to snipe at the enemy without exposing themselves over the parapet.
There were three standard ways to dig a trench: entrenching, sapping, and tunneling. Entrenching, where a man would stand on the surface and dig downwards, was most efficient, as it allowed a large digging party to dig the full length of the trench simultaneously. However, entrenching left the diggers exposed above ground and hence could only be carried out when free of observation, such as in a rear area or at night. Sapping involved extending the trench by digging away at the end face. The diggers were not exposed, but only one or two men could work on the trench at a time. Tunneling was like sapping except that a "roof" of soil was left in place while the trench line was established and then removed when the trench was ready to be occupied. The guidelines for British trench construction stated that it would take 450 men 6 hours (at night) to complete 250 m (275yd) of front-line trench system. Thereafter, the trench would require constant maintenance to prevent deterioration caused by weather or shelling.
The battlefield of Flanders, which saw some of the worst fighting, presented numerous problems for the practice of trench warfare, especially for the British, who were often compelled to occupy the low ground. Heavy shelling quickly destroyed the network of ditches and water channels which had previously drained this low-lying area of Belgium. In most places, the water table was only a meter or so below the surface, meaning that any trench dug in the ground would quickly flood. Consequently, many "trenches" in Flanders were actually above ground and constructed from massive breastworks of sandbags (actually filled with clay). Initially, both the parapet and parados of the trench were built in this way, but a later technique was to dispense with the parados for much of the trench line, thus exposing the rear of the trench to fire from the reserve line in case the front was breached.
The confined, static, and subterranean nature of trench warfare resulted in it developing its own peculiar form of geography. In the forward zone, the conventional transport infrastructure of roads and rail were replaced by the network of trenches and light tramways. The critical advantage that could be gained by holding the high ground meant that minor hills and ridges gained enormous significance. Many slight hills and valleys were so subtle as to have been nameless until the front line encroached upon them. Some hills were named for their height in meters, such as Hill 60. A farmhouse, windmill, quarry, or copse of trees would become the focus of a determined struggle simply because it was the largest identifiable feature. However, it would not take the artillery long to obliterate it, so that thereafter it became just a name on a map.
Battlefield features could be given a descriptive name ("Polygon Wood" near Ypres or "Lone Pine"), a whimsical name ("Sausage Valley" and "Mash Valley" on the Somme), a unit name ("Inniskilling Inch" at Helles named for the Royal Inniskilling Fusiliers) or the name of a soldier ("Monash Valley" at Anzac named after General John Monash). Prefixing a feature with "Dead Man's" was also popular for obvious reasons, such as "Dead Man's Road" leading in to Pozières, or "Dead Man's Ridge" at Anzac. There were numerous trench networks named "The Chessboard" or "The Gridiron" because of the pattern they described. For the Australians at Mouquet Farm, the advances were so short and the terrain so featureless that they were reduced to naming their objectives as "points" on the map, such as "Point 81" and "Point 55." Enemy trenches, which would become objectives in an attack, needed to be named as well. Many were named for some observed event such as "German Officers' Trench" at Anzac (where a couple of German officers were sighted) or "Ration Trench" on the Somme (where German ration-carrying parties were sighted). The British gave an alcoholic flavour to the German trenches in front of Ginchy: "Beer Trench," "Bitter Trench," "Hop Trench," "Ale Alley," and "Pilsen Trench." Other objectives were named according to their role in the trench system, such as the "Switch Trench" and "Intermediate Trench" on the Somme. Some sections of the British trench system read like a Monopoly board, with names such as "Park Lane" and "Bond Street," British regular divisions habitually named their trenches after units, which resulted in names such as "Munster Alley" (Royal Munster Fusiliers), "Black Watch Alley" (Black Watch Regiment) and "Border Barricade" (Border Regiment). The Anzacs tended to name features after soldiers ("Plugge's Plateau," "Walker's Ridge," "Quinn's Post," "Johnston's Jolly," "Russell's Top," "Brind's Road" and so forth).
An individual soldier's time in the front-line trench was usually brief; from as little as one day to as much as two weeks at a time before being relieved. The Australian 31st Battalion once spent 53 days in the line at Villers Bretonneux, but such a duration was a rare exception. A typical British soldier's year could be divided as follows:
Even when in the front line, the typical soldier would only be called upon to engage in fighting a handful of times a year—making an attack, defending against an attack or participating in a raid. The frequency of combat would increase for the men of the "elite" fighting divisions—on the Allied side; the British regular divisions, the Canadian Corps, the French XX Corps and the Anzacs.
Some sectors of the front saw little activity throughout the war, making life in the trenches comparatively easy. When the I Anzac Corps first arrived in France in April 1916 after the evacuation of Gallipoli, they were sent to a relatively peaceful sector south of Armentières to "acclimatise". Other sectors were in a perpetual state of violent activity. On the Western Front, Ypres was invariably hellish, especially for the British in the exposed, overlooked salient. However, quiet sectors still amassed daily casualties through sniper fire, artillery, disease, and poison gas. In the first six months of 1916, before the launch of the Somme Offensive, the British did not engage in any significant battles on their sector of the Western Front and yet suffered 107,776 casualties. About 1 in 8 men would return alive and wound free from the trenches.
A sector of the front would be allocated to an army corps, usually comprising three divisions. Of these two divisions would occupy adjacent sections of the front and the third would be in rest to the rear. This breakdown of duty would continue down through the army structure, so that within each front-line division, typically comprising three infantry brigades (regiments for the Germans), two brigades would occupy the front and the third would be in reserve. Within each front-line brigade, typically comprising four battalions, two battalions would occupy the front with two in reserve. And so on for companies and platoons. The lower down the structure this division of duty proceeded, the more frequently the units would rotate from front-line duty to support or reserve.
During the day, snipers and artillery observers in balloons made movement perilous, so the trenches were mostly quiet. Consequently, the trenches were busiest at night, when cover of darkness allowed the movement of troops and supplies, the maintenance and expansion of the barbed wire and trench system, and reconnaissance of the enemy's defenses. Sentries in listening posts out in no man's land would try to detect enemy patrols and working parties or indications that an attack was being prepared.
Pioneered by the PPCLI in February 1915, trench raids were carried out in order to capture prisoners and "booty"—letters and other documents to provide intelligence about the unit occupying the opposing trenches. As the war progressed, raiding became part of the general British policy, the intention being to maintain the fighting spirit of the troops and to deny no man's land to the Germans. As well, they were intended to force the enemy to reinforce, which exposed his troops to artillery fire. Such dominance was achieved at a high cost, when the enemy replied with his own artillery, and a post-war British analysis concluded the benefits were probably not worth the cost. Early in the war, surprise raids would be mounted, particularly by the Canadians, but increased vigilance made achieving surprise difficult as the war progressed. By 1916, raids were carefully planned exercises in combined arms and involved close co-operation of infantry and artillery. A raid would begin with an intense artillery bombardment designed to drive off or kill the front-trench garrison and cut the barbed wire. Then the bombardment would shift to form a "box", or cordon, around a section of the front line to prevent a counter-attack intercepting the raid. However, the bombardment also had the effect of notifying the enemy of the location of the planned attack, thus allowing reinforcements to be called in from wider sectors.
Medical services were primitive and antibiotics had not yet been discovered. Relatively minor injuries could prove fatal through onset of infection and gangrene. The Germans recorded that 15% of leg wounds and 25% of arm wounds resulted in death, mainly through infection. The Americans recorded 44% of casualties who developed gangrene died. 50% of those wounded in the head died and 99% of those wounded in the abdomen died. 75% of wounds came from shell fire. The wound resulting from a shell fragment was usually more traumatic than a gunshot wound. A shell fragment would often introduce debris, making it more likely that the wound would become infected. These factors meant a soldier was three times more likely to die from a shell wound to the chest than from a gunshot wound. The blast from shell explosions could also kill by concussion. In addition to the physical effects of shell fire, there was the psychological damage. Men who had to endure prolonged bombardment would often suffer debilitating shell shock, a condition not well understood at the time (it is now usually called post traumatic stress disorder).
As in many other wars, World War I's greatest killer was disease. Sanitary conditions in the trenches were quite poor, and common infections included dysentery, typhus, and cholera. Many soldiers suffered from parasites and related infections. Poor hygiene also led to fungal conditions, such as trench mouth and trench foot. Another common killer was exposure, since the temperature within a trench in the winter could easily fall below zero degrees Celsius (32 °F). Burial of the dead was usually a luxury that neither side could easily afford. The bodies would lie in no man's land until the front line moved, by which time the bodies were often unidentifiable. On some battlefields, such as at the Nek in Gallipoli, the bodies were not buried until after the war. On the Western Front, bodies continue to be found as fields are ploughed and building foundations dug.
At various times during the war—particularly early on—official truces were organised so that the wounded could be recovered from no man's land and the dead could be buried. Generally, senior commands disapproved of any slackening of the offensive for humanitarian reasons and so ordered their troops not to permit enemy stretcher-bearers to operate in no man's land. However, this order was almost invariably ignored by the soldiers in the trenches, who knew that it was to the mutual benefit of the fighting men of both sides to allow the wounded to be retrieved. So, as soon as hostilities ceased, parties of stretcher bearers, marked with Red Cross flags, would go out to recover the wounded, sometimes swapping enemy wounded for their own. There were occasions when this unofficial cease fire was exploited to conduct a reconnaissance or to reinforce or relieve a garrison. One famous truce was the Christmas truce between British and German soldiers in the winter of 1914 on the front near Armentieres. German soldiers began singing Christmas carols and soon soldiers left their trenches. The soldiers exchanged gifts and stories, and played several games of football. As mentioned previously, the commanders of the warring nations disapproved of this cease fire, and the British court-martialed several of their soldiers. The spirit of this truce is portrayed in the 2005 movie Merry Christmas (Joyeux Noël).''
The German counterpart to the Lee-Enfield was the 7.92x57mm (.323") Mauser Gewehr 98. It was less suited to rapid fire than the SMLE, due to its smaller magazine and slower rate of fire. The British soldier was equipped with a 21-inch (53 cm) sword bayonet, which was too long and unwieldy to be particularly effective in close-quarters combat. However, bayonet use was safer than firing the rifle which, in a mêlée, might strike an ally instead of an enemy. British figures recorded only 0.3% of wounds were caused by bayonets; however, a strike from a bayonet was likely to result in death. The bayonet was also used to finish off wounded enemy soldiers during an advance, both saving ammunition and reducing the probability of being attacked from the rear. Imperial German soldiers generally carried the S98/05 "Butcher-blade" bayonet, which was an effective weapon in the open, but like the British bayonet, difficult to use in the narrow trenches when attached to a rifle.
Many soldiers preferred a short-handled spade or entrenching tool over a bayonet. They would sharpen the blade so it was just as effective as a bayonet, and the shorter length made them handier to use in the confined quarters of the trenches. These tools could then be used to dig in after they had taken a trench. Since the troops were often not adequately equipped for trench warfare, improvised weapons were common in the first encounters, such as short wooden clubs and metal maces, as well as trench knives and brass knuckles (see trench raiding). As the war progressed, better equipment was issued, and improvised arms were discarded.
Used by American soldiers in the Western front, the pump action shotgun was a formidable weapon in short range combat, enough so that Germany lodged a formal protest against their use on 14 September 1918, stating "every prisoner found to have in his possession such guns or ammunition belonging thereto forfeits his life" (though this threat was apparently never carried out). The U.S. military began to issue models specially modified for combat, called "trench guns", with shorter barrels, higher capacity magazines, no choke, and often heat shields around the barrel, as well as lugs for the M1917 bayonets. ANZAC and some British soldiers were also known to use sawn-off shotguns in trench raids, because of their portability, effectiveness at close range, and ease of use in the confines of a trench. This practice was not officially sanctioned, and the shotguns used were invariably modified sporting guns.
The hand grenade came to be the primary infantry weapon of trench warfare. Both sides were quick to raise specialist bombing squads. The grenade enabled a soldier to engage the enemy without exposing himself to fire, and it did not require precise accuracy to kill or maim. The Germans and Turks were well equipped with grenades from the start of the war, but the British, who had ceased using grenadiers in the 1870s and did not anticipate a siege war, entered the conflict with virtually none, so soldiers had to improvise bombs with whatever was available. By late 1915, the British Mills bomb had entered wide circulation, and by the end of the war 75 million had been used.
The British High Command were less enthusiastic about machine guns, supposedly considering the weapon too "unsporting" and encouraging defensive fighting; and they lagged behind the Germans in adopting it. Field Marshall Sir Douglas Haig is quoted as saying in 1915, "The machine gun is a much overrated weapon; two per battalion is more than sufficient" , an attitude which resulted in record numbers of British casualties. In 1915 the Machine Gun Corps was formed to train and provide sufficient heavy machine gun teams. It was the Canadians that made the best practice, pioneering area denial and indirect fire (soon adopted by all Allied armies) under the guidance of former French Army Reserve officer Major General Raymond Brutinel. Minutes before the attack on Vimy Ridge the Canadians also thickened the artillery barrage by aiming machine guns at the precise angle to rain down on the Germans, they also significantly increased the amount of machine guns per battalion. To match demand, production of the Vickers machine gun was contracted to firms in the United States. By 1917, every company in the British forces were also equipped with four Lewis light machine guns, which significantly enhanced their firepower.
The heavy machine gun was a specialist weapon, and in a static trench system was employed in a scientific manner, with carefully calculated fields of fire, so that at a moment's notice an accurate burst could be fired at the enemy's parapet or a break in the wire. Equally it could be used as light artillery in bombarding distant trenches. Heavy machine guns required teams of up to eight men to move them, maintain them, and keep them supplied with ammunition. This made them impractical for offensive maneuvers, contributing to the stalemate on the Western Front.
The main British mortar was the Stokes, precursor of the modern mortar. It was a light mortar, but was easy to use, and capable of a rapid rate of fire by virtue of the propellant cartridge being attached to the shell. To fire the Stokes mortar, the round was simply dropped into the tube, where the cartridge was ignited automatically when it struck the firing pin at the bottom. The Germans used a range of mortars. The smallest were grenade-throwers (Granatenwerfer) which fired "pineapple" bombs. Their medium trench-mortars were called mine-throwers (Minenwerfer), dubbed "moaning minnies" by British Commonwealth troops. The heavy mortar was called the Ladungswerfer, which threw "aerial torpedoes", containing a 200lb (90 kg) charge to a range of 1000yd (914 m). The flight of the missile was so slow and leisurely men on the receiving end could make some attempt to seek shelter.
Artillery pieces were of two types: guns and howitzers. Guns fired high-velocity shells over a flat trajectory and were often used to deliver fragmentation and to cut barbed wire. Howitzers lofted the shell over a high trajectory so it plunged into the ground. The largest calibers were usually howitzers. The German 420 mm howitzer weighed 20 tons and could fire a one-ton shell over 10 km. A critical feature of period artillery pieces was the hydraulic recoil mechanism, which meant the gun did not need to be re-laid (re-aimed) after each shot. Initially each gun would need to register its aim on a known target, in view of an observer, in order to fire with precision during a battle. The process of gun registration would often alert the enemy an attack was being planned. Towards the end of 1917, artillery techniques were developed enabling fire to be delivered accurately without registration on the battlefield - the gun registration was done behind the lines then the pre-registered guns were brought up to the front for a surprise attack.
Tear gas was first employed in August 1914 by the French, but this could only disable the enemy. In April 1915, chlorine was first used by Germany at the Second Battle of Ypres. A large enough dose could kill, but the gas was easy to detect by scent and sight. Those that were not killed on exposure could suffer permanent lung damage. Phosgene, first used in December 1915, was the ultimate killing gas of World War I—it was 18 times more powerful than chlorine and much more difficult to detect. However, the most effective gas was mustard gas, introduced by Germany in July 1917. Mustard gas was not as fatal as phosgene, but it was hard to detect and lingered on the surface of the battlefield and so could inflict casualties over a long period. The burns it produced were so horrific that a casualty resulting from mustard gas exposure was unlikely to be fit to fight again. Only 2% of mustard gas casualties died, mainly from secondary infections.
The first method of employing gas was by releasing it from a cylinder when the wind was favourable. Such an approach was obviously prone to miscarry if the direction of the wind was misjudged. Also, the cylinders needed to be positioned in the front trenches where they were likely to be ruptured during a bombardment. Later in the war, gas was delivered by artillery or mortar shell.
At about the same time the British were developing their own helmets. The French design was rejected as not strong enough and too difficult to mass-produce. The design that was eventually approved by the British was the Brodie helmet (designed by John L. Brodie). This had a wide brim to protect the wearer from falling objects, but offered less protection to the wearer's neck. When the Americans entered the war, this was the helmet they chose, though some units used the French Adrian helmet. The traditional German pickelhaube was replaced by the Stahlhelm or "steel helmet" in 1916. Some elite Italian units used a helmet derived from ancient Roman designs. None of these standard helmets could protect the face or eyes, however. Special face-covers were designed to be used by machine-gunners, and the Belgians tried out goggles made of louvres to protect the eyes.
The French introduced the CSRG 1915 Chauchat during Spring 1916 around the concept of "Walking Fire", employed in 1918 when 250,000 weapons were fielded. More than 80,000 of the best shooters received the semi automatic RSC 1917 rifle allowing them rapid shooting at waves of attacking soldiers. Firing port weapons were installed in the newly arrived FT 1917 tanks.
The Allies sometimes used tanks to get the advantage in battle. Tanks were helpful in destroying the enemy's trenches. They could penetrate barbed wire, some could bridge trenches, and machine guns could not damage them; thus, they overcame the major obstacles of trench warfare. However, tanks of the period were very slow, very heavy, and often mechanically unreliable. Also, they were still vulnerable to artillery fire.
The French Army fielded a ground version of the Hotchkiss Canon de 37mm used by the French Navy. It was primarily used to destroy German machine gun nests and concrete reinforced pillboxes with high explosive rounds, but an armour piercing round was designed to defeat the German tanks, making it the first anti tank gun.
The Germans employed flame throwers (Flammenwerfer) during the war for the first time against the French on June, 25th, 1915, then against the British on July 30th in Hooge. The technology was in its infancy, and use was not very common until the end of 1917 when portability and reliability were improved. It was used in more than 300 documented battles. In 1918, it became a weapon of choice for Stosstruppen with a team of six "Pionieren" per squad.
A new type of machine gun was introduced in 1916. Initially an aircraft weapon, the Bergmann LMG 15 was modified for ground use, with the later dedicated ground version being the LMG 15 n.A. It was used as an infantry weapon on all European and Middle Eastern fronts until the end of World War 1. It later inspired the MG 30 and the MG 34 as well as the concept of the general purpose machine gun.
What became known as the submachine gun had its genesis in WWI, developed around the concepts of infiltration and fire and movement, specifically to clear trenches of enemy soldiers when engagements were unlikely to occur beyond a range of a few feet. The MP18 was the first practical submachine gun used in combat. It was fielded in 1918 by the German Army as the primary weapon of the Stosstruppen, assault groups that specialized in trench combat. Its design was the base of most of the submachine guns between 1920 and 1960. The firepower of this new class of weapons made such an impression on the Allies that the Treaty of Versailles banned further study and manufacture of such light automatic firearms.
If the miners detected an enemy tunnel in progress, they would often drive a counter-tunnel, called a counter-mine or camouflet, which would be detonated in an attempt to destroy the other tunnel prematurely. Night raids were also conducted with the sole purpose of destroying the enemy's mine workings. On occasion, mines would cross and fighting would occur underground. The mining skills could also be used to move troops unseen. On one occasion a whole British division was moved through interconnected workings and sewers without German observation. The British detonated a number of mines on July 1, 1916, the first day of the Battle of the Somme. The largest mines—the Y Sap Mine and the Lochnagar Mine—each containing 24 tons of explosives, were blown near La Boiselle, throwing earth 4,000 feet into the air.
At 3.10 AM on June 7, 1917, 19 mines were detonated by the British to launch the Battle of Messines. The average mine contained 21 tons of explosive and the largest, 125 feet beneath Saint-Eloi, was twice the average at 42 tons. The combined force of the explosions was supposedly felt in England. As remarked by General Plumer to his staff the evening before the attack:
The craters from these and many other mines on the Western Front are still visible today. Three further mines were laid for Messines but were not detonated as the tactical situation had since changed. One blew during a thunderstorm in 1955; the other two remain to this day.
The popular image of a trench assault is of a wave of soldiers, bayonets fixed, going "over the top" and marching in a line across no man's land into a hail of enemy fire. This attaque à outrance was indeed the standard method early in the war and successful examples are few. The more common tactic was to attack at night from an advanced post in no man's land, having cut the barbed wire entanglements beforehand. In 1917, the Germans innovated with infiltration tactics where small groups of highly trained and well-equipped troops would attack vulnerable points and bypass strong points, driving deep into the rear areas. The distance they could advance was still limited by their ability to supply and communicate.
The role of artillery in an infantry attack was twofold. The first aim of a barrage was to prepare the ground for an infantry assault killing or demoralising the enemy garrison and destroying his defences. The amount of time these initial barrages lasted for was varied, ranging from seconds to days. The problem with artillery bombardments prior to infantry assaults was that they were often ineffective at destroying enemy defences and only served to provide the enemy with advanced notice that an attack was imminent. The British barrage that began the Battle of the Somme lasted eight days but did little damage to either the German's barbed wire or their heavily-fortified concrete bunkers where the defenders were able to see out the bombardment safely. Once the guns stopped the defenders knew that the infantry were about to emerge and were usually ready for them. The second aim was to protect the attacking infantry by providing an impenetrable "barrage" or curtain of shells to prevent an enemy counter-attack. The first attempt at sophistication was the "lifting barrage" where the first objective of an attack was intensely bombarded for a period before the entire barrage "lifted" to fall on a second objective farther back. However, this usually expected too much of the infantry, and the usual outcome was that the barrage would outpace the attackers, leaving them without protection. This resulted in the use of the "creeping barrage" which would lift more frequently but in smaller steps, sweeping the ground ahead and moving so slowly that the attackers could usually follow closely behind it. Capturing the objective was half of the battle, but the battle was only won if the objective was held. The attacking force would have to advance with not only the weapons required to capture a trench but also the tools—sandbags, picks and shovels, barbed wire—to fortify and defend from counter-attack. The Germans placed great emphasis on immediately counter-attacking to regain lost ground. This strategy cost them dearly in 1917 when the British started to limit their advances so as to be able to meet the anticipated counter-attack from a position of strength. Part of the British artillery was positioned close behind the original start line and took no part in the initial bombardment, being saved to support the advancing troops as they moved beyond the range of guns further back.
Conceived to provide protection from fire, tanks added mobility, as well. As the Allied forces perfected them, they broke the deadlock. While not effectively employed at first, tanks had tremendous morale effects on German troops in the closing stages of the war on the Western front. The average infantryman had no anti-tank capability, and there were no specialized anti-tank guns. Once tanks began to be used in concentrations, they easily broke through German lines and could not be dislodged through infantry counterattack.
During the last 100 days of World War I, the British forces broke through the German trench system and harried the Germans back toward Germany using infantry supported by tanks and close air support. Between the two world wars these techniques were used by J.F.C. Fuller and B.H. Liddell Hart to develop theories about a new type of warfare. The ideas were picked up by the Germans, who developed them further and put them into practice as blitzkrieg.
The stunning victories by the Germans early in World War II using blitzkrieg showed fixed fortifications like the Maginot Line were worthless if there was room to circumvent them. At Sevastopol, Red Army forces successfully held trench systems on the narrow peninsula for several months against intense German bombardment. The Western Allies in 1944 broke through the (incomplete) Atlantic Wall with relative ease through a combination of amphibious landings, naval gunfire, air attack, and airborne landings. Combined arms tactics (where infantry, artillery, armour and aircraft operate in close cooperation) made trench warfare a thing of the past.
This is not to say entrenchment is redundant. It is still a valuable method for reinforcing natural obstacles to create a line of defence. For example, before the start of the Battle of Kursk, the Soviets constructed a system of defence more elaborate than any other they built during World War II. These defences succeeded in stopping the German armoured pincers meeting and enveloping the salient. Also, at the start of the Battle of Berlin, the last major assault of World War II, the Russians attacked over the river Oder against German troops dug in on the Seelow Heights, about 50 km (30 mi) east of Berlin. Entrenchment allowed the Germans, who were massively outnumbered, to survive a barrage from the largest concentration of artillery in history; as the Red Army attempted to cross the marshy riverside terrain, they lost tens of thousands of casualties to the entrenched Germans before breaking through.
Trench warfare has been very infrequent since the end of World War I. When two large armoured armies meet, the result has generally been mobile warfare of the type which developed in World War II. However, trench warfare reemerged in the latter stages of the Chinese Civil War (Huaihai Campaign), Korean War and in some locations and engagements in the Vietnam War. During the Cold War, NATO forces routinely trained to fight through extensive works called "Soviet-style trench systems", named after the Warsaw Pact's complex systems of field fortifications, an extension of Soviet field entrenching practices for which they were famous in their Great Patriotic War.
Although mainly a siege, it was not unusual to find an extensive trench system inside and outside the city of Sarajevo during the siege of 1992–1996. It was used mainly for transportation to the frontline or to avoid some of the snipers inside of the city. Any pre-existing structures were used as trenches, the best known example is the bobsleigh course on Trebević, which was used by both Serb and Bosniak during the siege. Another example of trench stalemate was the Eritrean-Ethiopian War of 1998–2002. The front line in Korea and the front lines between Pakistan and India in Kashmir are two examples of demarcation lines which could become hot at any time. They consist of kilometers of trenches linking fortified strongpoints and in Korea surrounded by millions of land mines.