Trench warfare was not a new phenomenon in World War I. Earthworks were employed in such conflicts as the Crimean War and the American Civil War, most famously at the sieges of Sevastopol and Petersburg. In World War I, however, advances in technology and organizational ability extended the use of trenches far beyond these smaller examples. As Winston Churchill described it, here were “[r]amparts more than 350 miles long, ceaselessly guarded by millions of men, sustained by thousands of cannon.” World War I transformed a defensive expedient into the defining characteristic of four years of conflict.
In the nineteenth century, defensive experts focused on the creation of concrete strongpoints defended by heavy artillery. The days of singular fortresses were past, but by arranging multiple strongpoints in positions that offered overlapping fields of fire, they hoped to fend off the modern infantry. The relative successes of the French forts at Verdun suggest that this was a valid approach, especially when one considers that they held off the Germans even without the heavy artillery that was originally meant for their defense.
Still, the lavishly prepared defensive positions had limited value during World War I for the main reason that the battles were rarely fought there. With the exceptions of the fortifications at Liege and Verdun, in which the Germans specifically attacked such targets, these were not the typical battle sites. The course of the fighting in 1914 had created circumstances in which the Western Front extended from Switzerland to the English Channel. Each side had endeavored to turn the other side’s flank, only to find that these flanks extended ever northward until both sides ran out of land. During these early conflicts, primitive trenches were dug on a local basis to offer the defenders some measure of protection. Strategic considerations perpetuated and magnified this tendency.
When the Schlieffen Plan failed, the Germans settled into a defensive strategy in the west; indeed, they undertook no major offensives in the west until after the surrender of Russia, with the sole exception of the Verdun campaign, which was undertaken in an effort to cripple the French Army, rather than to take the territory. Germany’s strategic problem had always been the prospect of being trapped between two enemy camps; the Schlieffen Plan had been created to defeat these two camps in sequence, crushing France before Russia could become a major threat. This effort failed, and German planners proceeded to reverse the plan, holding the Western Allies at bay while trying to knock Russia out of the war.
With this in mind, the Germans were content to hold territories taken in 1914 and wait for a decisive change in the circumstances. For the same reasons, such passivity was unacceptable for the Western Allies, who undertook numerous, often ruinous, offensives in an effort to dislodge the Germans. Still, forces in the field needed to be protected while the resources were gathered for a new offensive, and a certain amount of cover was necessary to mask French and British intentions before the assault was launched. Thus, each side had ample reason to build upon these primitive trenches and extend them into an organized network of defenses. In basic form, the trenches were largely the same, with the main difference being that German trenches were built with the intention of long-term residency, while those of the Entente had a more temporary quality.
In either case, the trenches were organized along the same lines that had animated fortress construction in the previous age. It was no longer feasible for a single wall to hold out the enemy, no matter how strongly it might be constructed, and so the emphasis was on multiple strongpoints that offered overlapping fields of fire. In the forward areas, this sometimes included isolated positions with good visibility facing the enemy line, but the main line of trenches needed to be connected to each other to facilitate the movement of men without exposing them to the dual hazards of machine gun fire and artillery fire. Moreover, there needed to be inner zones where the men might wait in relative safety during a heavy artillery barrage, but then from which they could emerge when the guns fell silent and an enemy assault could be expected. As a result, a fairly sophisticated network of trenches was built.
In the early years of the war, tactical depth and ease of movement were assured by building two or three parallel lines of trench, with additional lines between them to facilitate movement. The outermost trench was considered the firing line. In early British use, the second line was a cover trench, while the German system had a middle zone intended for support and the hintermost line was available for reserve troops. It should be noted, however, that an enemy success in attacking the outer trench turned the support trench into a new front line. The multiple lines of defense were as important for maintaining the integrity of the overall system in the face of limited enemy successes as they were for protecting support and reserve troops until they were needed for front-line use.
In this system, the strongpoints with overlapping fields of fire were provided by forward sections of trench that operated much like foxholes, except that they were connected to each other by recessed lines of trench called “traverses.” Seen from the sky, this alternating pattern of forward lines and recessed lines look like the crenellations at the top of the wall on a medieval castle. Communications trenches, leading from one line of trench to the next, tended to be dug at diagonal lines, hindering fields of fire for attacking enemy troops trying to seize control of the outer trench. Other passages led down into dugout rooms for protection during artillery barrages.
In the latter period of the war, following the colossal battles of 1916, even greater depth was built into the trench system, with an extreme forward zone consisting of small outposts, followed by a front line that offered good fields of fire for the machine guns, but were not arranged in one continuous line. Only the middle and rear zones offered continuous lines, and these zones might each consist of more than one trench line. Such rear zones offered greater security, and it was here that the heavy artillery was sited. It was also possible in many cases to reinforce strongpoints here with concrete.
Most trenches were dug into the earth, however, and prone to collapse when wet or when disturbed by heavy artillery blasts. Wood and sandbags were both used as extensively as possible to shore up the trenches. These were not always available in desired quantities, however, and furthermore, extensive artillery fire defeated such work in many lines of trench. Mud was a perpetual factor in World War I combat, and after a battle had concluded, substantial repair was often necessary.
The primary danger to men in the trenches was an outright offensive. To the defender, this usually entailed a heavy preliminary artillery attack, which was often largely thwarted by taking cover, followed by large numbers of enemy soldiers climbing up from the trenches, crossing the various obstacles in the contested zone, and trying to overwhelm the front lines by superior numbers. On the strategic level, this rarely worked very well, but it could enjoy some local successes. For the attacker, this same exposed attack represented an even greater danger, especially when the artillery failed to knock out many of the enemy’s machine guns. In the later phases of the war, tanks and air attack added to the dangers of the soldiers in the trenches.
Other hazards occurred more regularly. Soldiers in the front line undertook night patrols on a rotating basis; between two and seven soldiers crossed “No Man’s Land,” sometimes to observe the enemy trenches, and sometimes to make a limited attack, generally to collect a prisoner or otherwise to acquire some useful intelligence.
Stealth was necessary in such raids, and so the soldiers involved often resorted to quiet weapons like clubs and knives. This highlights another facet of trench warfare: the use of the available technology. On the one hand, the stagnation of the trenches inspired the development of new technologies, from airplanes built to facilitate more effective ground attack, to the creation of tanks and subsequently of anti-tank guns. The development of submachine guns or machine pistols was a part of this trend.
At the same time, the trenches also inspired the revival of technologies previously considered obsolete. Steel helmets, discarded in the eighteenth century by most infantry soldiers, returned in 1916 in most armies. Grenades, which fell out of use in the nineteenth century, again became viable when they could be hurled into an enemy trench. Mortars found a new use in miniaturized form, suitable for firing from inside a trench. Shotguns, clubs and knives found a new military use in the trenches.
Ellis, John. Eye-Deep in Hell: Trench Warfare in World War I. Johns Hopkins, 1989
Haythornthwaite, Philip J. The World War One Source Book. Arms & Armour, 1996
Johnson, J.H. Stalemate!: The Great Trench Warfare Battles 1915-1917. Orion, 1999
Sheffield, Gary. War on the Western Front: In the Trenches of World War I. Osprey, 2008
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