Trench Warfare

Pictures of trenches are often used to symbolize the First World War: indeed it is rare to see an image from the conflict that does not include men in trenches, or a battle scarred landscape with trenches in it. Furthermore, understanding the role trenches played in the conflict is critical to understanding the nature and destructiveness of the war, yet relatively little is understood about their use. In order to explain why trenches were so important it is necessary to ask several questions. What are trenches? Why did soldiers need them? How did they change over time? What effect did all of this have on the battlefield? It is the interaction of the answers to these questions that helps to explain why trenches were so important and why the war was such a long bloody deadlock.

A trench is a ditch dug almost entirely into the ground, with the earth from the ditch thrown up onto the surface just high enough to protect the head of a soldier occupying it. As such a trench was typically at least as deep as a man was tall (roughly two meters), in order to keep him out of the line of an enemy’s fire. The trench systems of the First World War typically consisted of multiple lines of trenches stretched as far as it was possible to man and supply them. On the Western Front this meant trenches stretched from the Swiss border to the English Channel, a distance of some four hundred miles. Elsewhere, they were not always continuous but they were still used extensively and over great distances.

Soldiers needed trenches for the following main reasons: to provide them with physical protection; to enhance their ability to fight, both of which in turn allowed smaller numbers of men to defend against greater numbers of their enemy; and to dominate an area.¹ The trenches protected soldiers by providing a physical barrier, made of earth, that stood between them and someone firing at them with rifles, machine guns, or artillery. Being below the level of the ground meant that a soldier was relatively safe from enemy fire. This protection, in turn, made it easier for soldiers to stand and fight in a battle. Furthermore, fewer soldiers were needed to defend any particular area of the front line because the trench’s protection made them more difficult to kill. In turn,  more enemy soldiers with more guns were needed to successfully capture a trench than would be the case otherwise. Thus, unlike in previous wars, enormous armies could hold ground over great distances and they were relatively well protected in the process.

Prior to the development of trenches, soldiers had used breastworks (sometimes called  entrenchments). These consisted of a roughly one-meter high barrier made primarily of earth that a soldier had thrown in front of a shallow dug ditch. This style of fortification had existed since Roman times, if not earlier, and was still effective against firearms into the mid-nineteenth century. However, the massive increase in firepower that came with the second industrial revolution of the latter half of the nineteenth century meant that breastworks, and anything like them, were no longer sufficient to protect soldiers. In response soldiers started to dig further into the ground, and as the shallow ditches got deeper they became trenches. In order to move around without being exposed to an enemy’s fire, these trenches were connected and came to form the extended trench lines of the First World War. With the enormous improvements in airplanes during the first part of the twentieth century, these long lines of trench were relatively easy to see. Furthermore, once they were dug they could not be moved. At the beginning of the war, this was not such a problem as the armies lacked sufficient numbers of artillery pieces to inflict the kind of damage necessary to kill men sheltering and fighting in trenches. However, once the armies of the First World War had built and deployed large numbers of artillery pieces, particularly big ones, trench lines became extremely vulnerable to enemy artillery fire. As more and bigger artillery became available the armies needed to change how they used and built trenches. 

Early in the war (using the Western Front as our example) a trench system might consist of 2-3 parallel trenches about 250-350 meters apart. Thus an early-war trench system might be 500-1000 m from front to back. The increase in artillery meant that by 1917 a typical trench system consisted of 4-5 zones; an outpost zone of 500-1000 m made up of short unconnected trenches; behind that would be the ‘front line’ of 2-3 parallel trenches about 150-250 m apart (not necessarily continuous); a battle zone of at least 2,000 m with multiple small unconnected trenches and bunkers; an artillery protective line of two more parallel lines of trenches; and the rearward zone which might extend several thousand meters further back.² Thus, an entire late-war trench system was typically 6-8,000 m and sometimes as much as 15,000 m from font to back.

All of this is significant because the increasing space occupied by a defending army, especially when combined with the effective protection provided by trenches, meant that ever more artillery and ammunition, some 1.45 billion projectiles in all³, were needed to deal with the problem of defeating a defender. Any increase in the number and size of artillery saw a corresponding change in the way a defender built and arranged his trench system. This in turn meant more and bigger guns were needed to defeat him. This symbiotic relationship between trench systems and enemy artillery was the main reason for the four years of relative deadlock. This is partly so, because it took a lot of time and effort just to accumulate sufficient stocks of guns, ammunition, and men to launch an attack. This allowed a defender more time to prepare his trench system making it more difficult to attack, which meant there was a need for more artillery and ammunition, and more shelling. The consequences of all of this were: relative stalemate for much of the war on most fronts, enormous casualties from artillery fire, and unprecedented levels of damage to the landscape, some of which is still plainly visible today.⁴

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¹ Nicholas Murray, The Rocky Road to the Great War: the evolution of trench warfare to 1914, Potomac Books Inc., Washington D.C., 2013, pp. 22-39. Currently, there are really only two books that directly deal with this topic in full. The author’s own (see above), and Anthony Saunders much broader survey, Trench Warfare 1850-1950, Pen and Sword Military, Barnsley, United Kingdom, 2010.
² Captain G. C. Wynne, “The Development of the German Defensive Battle in 1917, and its Influence on British Defense Tactics, Part II” The Army Quarterly, Vol. 34, No. 2, July 1937, pp. 248-266. The other part of the article is: Captain G. C. Wynne, “The Development of the German Defensive Battle in 1917, and its Influence on British Defense Tactics, Part I” The Army Quarterly, Vol. 34, No. 1, April 1937, pp. 15-32.
³ The Belgian Explosive Ordnance Disposal Company still receives 2,000 calls per year related to unexploded artillery shells. From an article by Martin Fletcher, “Lethal Relics from WWI are still Emerging”, Daily Telegraph, 12 July 2013. http://www.telegraph.co.uk/history/britain-at-war/10172232/Lethal-relics-from-WW1-are-still-emerging.html (accessed: 5 February 2015).
⁴ It is also worth looking at photographs twelve and thirty-six in Alan Taylor, “World War I in Photos: a Century Later”, The Atlantic, 29 June, 2014. http://www.theatlantic.com/static/infocus/wwi/century/ (accessed: 5 February 2015).