♦  Trench Warfare on the Western Front 

Great War Special Studies Series


Aerial photo showing a section of the German Army's 1917-18 Siegfried Position. Belts of barbed wire are visible at the top of the photo. The main trench lines are connected to one another and to the rear by communication trenches. The trenches were used as supply dumps and billets for the troops manning the line; in action the defenders manned concealed dugouts and bunkers between and behind the trenches, covering all approaches to the position (Australian War Memorial)

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Trench warfare, that enduring symbol of the Great War, was the product of a century of political, economic, social and cultural development that transformed the military art. The large increase in Europe's population between 1800 and 1900 provided ample manpower for the new mass armies, while industry developed and produced in vast numbers new and deadly weapons of war: the magazine rifle, the machine gun and the breach-loaded recoil-stabilized cannon. Modern methods of administration and finance facilitated national mobilization and conscription, and enabled the armies to be supplied and maintained in the field indefinitely. Strategic mobility (the ability to move large bodies of troops from area to area) was provided by the railroad and an increasingly dense road net.

But once on the battlefield itself the armies of 1914 were no more mobile than those of the Napoleonic wars, moving on foot or horseback. Low mobility and high firepower gave the defender an overwhelming advantage, especially once the armies’ leaders grasped the value of entrenchment. Even the most hastily constructed field fortifications multiplied a soldier’s chances of survival in combat—thus the trench systems on both sides grew increasingly elaborate and complex. Moreover, the rival armies were fighting over the same small area of Western Europe where so many wars of the eighteenth and nineteenth centuries had been fought. But now they were many times larger, armed with much more lethal weapons, supported by mobilized national economies. The result, as indeed a few military thinkers had foreseen before 1914, was tactical, hence strategic, stalemate.

After the brief period of mobile warfare in 1914, trench warfare on the Western Front settled into a fairly standard pattern. On both sides the defense was usually based on three lines of trenches: a forward line, a support line and a rear line. The trenches were dug in a zigzag traverse pattern—this to prevent attackers in occupation of one section from firing straight down the trench—with firing steps for riflemen plus protected positions for machine guns and observation posts. Dugouts in the rear face of each trench provided accommodation for company and battalion headquarters, supply dumps, and shelter from artillery bombardment. The front-line trench was protected by barbed-wire entanglements many yards deep; the support line and the rear line served as assembly points for reserves and fallback positions for the front-line troops. The trenches were connected to one another and to the rear area by communications trenches. These enabled troops and supplies to be moved back and forth without exposure to enemy observation and fire.

British troops in a front-line trench (Imperial War Museum)

Behind the trench lines were troop billets, artillery positions and brigade headquarters. Farther back still were division and corps headquarters, large supply dumps, rest camps, field hospitals—all the supporting infrastructure required by modern armies. Infantry battalions typically rotated between the trenches, the billets and the rest camps. In sectors where an offensive was to take place, the rear areas of both sides would become crowded with reserves and vast quantities of supplies—especially the hundreds of thousands of rounds of artillery ammunition deemed necessary to support or resist the “big push.”

Senior commanders on both sides realized the inherent power of trench defenses, but that did not lead them to conclude that offensive action was futile. The search therefore began for some means of breaking the trench stalemate, and the most obvious solution seemed to be firepower. On the Allied side, the generals reasoned that with enough artillery the enemy’s trench defenses could be battered down, opening a way to the green fields beyond. The costly and unsuccessful Allied offensives on the Western Front in 1915 and 1916, culminating with the horrific Battle of the Somme, only served to confirm this view. The attacks, it was argued, had failed because the supporting artillery was insufficient. More was needed—enough to physically annihilate the enemy’s defense system in the sector of the attack.

In fact, however, the French and British generals had misdiagnosed the problem that confronted them.

It was certainly possible to break into the enemy's defenses, capturing a few lines of trenches, and indeed this happened fairly often. But it proved extraordinarily difficult to convert such a break-in to a full breakthrough. One obvious problem was that the laborious preparations for a major attack were easy to detect, so that the element of surprise was lacking. Thus forewarned, the defender had ample time to reinforce the threatened sector. And once the offensive began, the attacking troops of the first wave could be expected to do no more than make good the break-in—an effort that would decimate and exhaust them. The transition to a full breakthrough required the commitment of reserves—and the defender’s advantage in the management of reserves was the real reason for the costly failure of all offensives attempted by the Allies between 1914 and 1917.

Department of History, USMA West Point

Before sending their reserves forward, the generals at their division, corps and army headquarters needed accurate information from the front-line units: Where had the attack succeeded; where had it failed? But such information was slow to arrive. The primitive radios of the day were too cumbersome to carry forward with the attacking troops, telephone lines were all too easily cut by shellfire, messengers could be killed, wounded, or simply become lost. And when accurate information finally did come to hand, the attacker’s reserves had to struggle forward over ground devestated by prolonged artillery bombardment. Meantime the defender could shift reserves quickly by road and rail to the threatened sector of his front. For both sides the battle became a race against time—a race usually won by the defender.

But if the attacker suffered heavy casualties for nugatory gains, it was also true that the price of a successful defense was high. Holding the front-line trenches meant packing them with troops, who were therefore exposed for a prolonged period to the fury of bombardment. The Battle of the Somme in the summer of 1916 is remembered as a disaster for the British Army; less often remarked upon is its effect on the German Army. The precise toll on the German side is still a matter of some dispute, but a figure of 500,000 total casualties cannot be far from the mark. Toward the end of the battle, reports reaching OHL (the Supreme Command) indicated that the Somme defenses were close to collapse, the trench system itself in poor condition, the troops manning it worn out and dispirited.

The Germans thus realized that a new scheme of defense was required, and with characteristic efficiency and attention to detail they created one that proved highly effective in the conditions prevailing on the Western Front. Having studied the tactical lessons of the Russo-Japanese War (1904-05), the German Army had been the first to appreciate the value of field fortifications and they took advantage of wartime experience to further refine their methods. In the new defensive system that the German Army began to develop in 1916, strongly garrisoned linear trenches were no longer to be the principal fighting positions. The forward line of defense was now an outpost position, lightly held, whose function was to identify the attacker’s axis of advance and slow him down. The troops manning this outpost line occupied small dugouts, sited so as to take advantage of natural terrain features, and were connected to the rear area by communications trenches.

British heavy artillery in action (Imperial War Museum)

The main defensive zone was based on a series of mutually supporting strongpoints, held in platoon or company strength, sited to dominate all avenues of approach. Advancing between them, the attacking infantry found themselves exposed to withering rifle and machine gun fire, supplemented by pre-registered artillery and mortar barrages. The strongpoints were constructed of steel-reinforced concrete, making them invulnerable to all but a direct hit by heavy artillery. Throughout the defensive zone, barbed-wire entanglements and other obstacles were sited to slow the enemy down and prolong his exposure to the defenders’ fire. Behind the zone of strongpoints the Germans posted local reserves usually in company or battalion strength, whose task was to launch immediate counterattacks against any enemy troops who threatened to capture ground essential for the maintenance of the defense. Finally, there was the general reserve: so-called relief divisions (Ablösungsdivisionen), standing by in readiness to mount a full-scale counterattack if necessary. The depth of the main defensive zone was from three to four and a half miles, depending on the terrain.

To streamline command and control, the front was divided into sectors, in each of which a corps headquarters was made responsible for administrative and logistical tasks. Divisions were rotated in and out of these sectors as necessary, with tactical control devolved upon regimental and battalion commanders (Kampftruppenkommandeur) in the battle zone. These commanders were given discretion to maneuver their troops as necessary to deliver local counterattacks or evade enemy fire.

Further enhancing the effectiveness of their defensive system, the Germans were usually willing to yield ground that might be difficult to defend, siting their positions on the most advantageous terrain. In 1917 they even carried out a large-scale withdrawal from the Somme to the Siegfriedstellung (Siegfried Position), called the Hindenburg Line by the Allies. This position, which became the keystone of the German defenses on the Western Front, embodied all the principles mentioned above and took five months to construct. Though commanders were by no means agreed as to the advisability of abandoning the Somme line, the course of the battle from September to November seemed to leave no other option. In March 1917 the withdrawal to the Siegfriedstellung, code-named Alberich Bewegung (Operation Alberich) after the evil dwarf in the Nibelungenlied, was carried out in good order. It shortened the German line by some 25 miles, enabling a dozen divisions to be taken out of the front as reserves. Similar defensive positions were established for other sectors of the front in preparation for the anticipated defensive battles of 1917, for instance the Flandernstellung in Belgium. The new system of defense proved highly effective, frustrating the French and British offensives on the Aisne and in Flanders. Though they scored some tactical successes in the former offensive the Allies were unable to achieve a breakthrough, and they suffered 350,000 casualties against 163,000 inflicted on the Germans—a disappointment that touched off a large-scale mutiny in the ranks of the French Army. In Flanders, the Third Battle of Ypres was ended on a similar note of frustration.

The German withdrawal to the Siegfried Position, indicated by the dashed line (Wikimedia Commons)

In 1918 the trench deadlock on the Western Front was finally broken, first by by the German Army's new tactics (the hurricane artillery bombardment, specially trained assault troops, combined-armed battle groups), then by the Allies’ employment of the tank on a large scale against an exhausted enemy. In both cases, the effect was to restore tactical battlefield mobility. But though a few visionary military thinkers perceived that those final battles heralded another revolution in the art of war, the memory of the Western Front’s blood-soaked, trench-scarred battlefields remained dominant in the minds of soldiers, politicians and the European peoples for the next twenty years. One of them was a German soldier who’d served in the trenches for four years, and who on Armistice Day was lying in a military hospital, having been blinded by mustard gas. His name was Adolf Hitler.

Adolf Hitler (right) and comrades of the 16th Bavarian Reserve Infantry Regiment, circa 1916 (Bundesarchiv)

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