The history of the two sides’ strategies from 1915 to spring 1917 was one of frustration and failure. To explain why, it is necessary to re-examine how the battles were fought: how the troops and their equipment were deployed, and what weapons were available. An impasse at the level of tactics drove the two sides towards more ruthless strategies: the Allies towards escalating doses of attrition and the Germans towards Verdun and unrestricted submarine warfare. But this was not a static equilibrium, and both attackers and defenders were increasing their tactical sophistication and the number and power of the weapons at their disposal. Developments were in progress that after 1917 would break the stalemate. The emphasis here will be first on the conditions of defence and attack in the west, and then on a consideration of how far these conditions also held good elsewhere.
The Western Front has been likened to the outworks of the Roman Empire and the Iron Curtain that bisected Cold War Europe, but really it was without historical parallel. The trenches at the siege of Petersburg, in the closing stages of the American Civil War, were fifty-three miles long; but both they and those round Mukden in the Russo-Japanese War were eventually outflanked. In contrast the Western Front extended for some 475 miles and could not be outflanked, short of violating Dutch or Swiss neutrality, or by an Allied landing in Flanders. From the end of 1914 until 1918 it moved, with the exception of Germany’s voluntary withdrawal to the Hindenburg Line, barely more than five miles in either direction. It was also the most decisive and intractable front, where more troops and guns were concentrated than in any other theatre, and the graveyard not only of Falkenhayn’s grand design at Verdun but also of successive Allied initiatives in Champagne, on the Somme, and on the Chemin des Dames.
The ultimate defence was the infantry: German, French, and British Empire soldiers all displaying a stubbornness and resilience that many Russian and Austro-Hungarian units lacked. As all three armies showed comparable determination in attacking, however, the morale variable mattered less than on other fronts or in later periods of the war. The Western Front was distinctive not only for the troops’ fighting qualities but also for their numbers. The French and German armies were several times their size in 1870, and a huge British army later joined them. Each side mustered some 5,000 troops per mile of front, enough to garrison it thickly and to hold counter-attack forces in reserve. It helped that the more rugged and forested southernmost hundred miles was less suitable for large-scale operations and saw little fighting apart from a series of French attacks in the Vosges mountains in 1915. Even between Verdun and Ypres many sectors were quiet and never saw great battles. The most active sectors were in Flanders and on the two flanks of the Noyon bulge in Artois and Champagne. Although the high force-to-space ratio was an essential reason for the Western Front’s immobility, however, it must be considered in conjunction with the field fortifications and their supporting infrastructure, the weapons used to hold them, and defensive tactics.
The Germans took the initiative in creating the trench system. Trenches might be claustrophobic, verminous, smelly, wet, and cold, but they offered the best protection available against blast and bullets, and they saved lives. Most of the armies suffered their heaviest proportionate losses during the mobile campaigning of the first weeks of war. Digging in gave Germany a glacis for its western border while consolidating its grip on France and almost all of Belgium, either to keep in perpetuity or to trade in. It released forces to attack elsewhere, at Ypres in autumn 1914 or later in Poland and Serbia, and OHL endorsed it as a lesser evil that would at least halt the Allies’ advance.
In January 1915 Falkenhayn directed that the line must be so organized that a small force could hold it for a long time against superior numbers. A strong first position must be the backbone of resistance, to be held at all costs and at once retaken if any part of it were captured. Linked to it by communication trenches should be a second line, to shelter the garrison when the first was bombarded. Further lines to the rear should be beyond the range of enemy field guns. Falkenhayn wanted to lessen casualties by keeping the front-line cover thin, but if the main garrison were too far back the advanced guard would be more likely to surrender and the artillery could not protect them. Some of his commanders opposed a second line in principle, as making the defence of the first less stubborn. In the light of experience OHL nevertheless ordered in May that a reserve line must be built 2–3,000 yards behind the first along the entire front: a colossal undertaking that was completed by the end of the year. The Germans had the advantage of being able to select higher and drier ground, with good digging and above the water table, which lent itself to artillery observation. The great battles in Champagne, on the Somme, and at Arras therefore consisted of Allied attacks uphill against defences that by 1916–17 were up to 4–5,000 yards in depth, against the 1,000 yards characteristic of British ones. Those on the Somme, which followed Falkenhayn’s prescriptions closely, lay behind two belts of barbed wire, each three to five feet high and thirty yards deep. The ‘front line’ actually comprised three trenches 150 to 200 yards apart, the first for sentry groups, the second for the main garrison, and the third for support troops. The Germans’ forward trenches (like British ones) were not straight but set in every ten yards or so in a ‘traverse’, or dog-leg, that protected troops against shell blasts or enfilading fire if the enemy captured a portion of the line. They built deeper dug-outs: six to nine feet down in 1915 and twenty-five to thirty feet on the Somme. A thousand yards behind the first position lay an intermediate line of machine-gun strongpoints; and behind that communication trenches led to the reserve position (the ‘second line’ of Falkenhayn’s memorandum), as heavily wired as the first and out of range of the Allied artillery, which would therefore need to be moved up to support an assault on it. Another 3,000 yards back lay the third position, added after the experience of September 1915, when the French had reached the German second line. Telephone cables laid six or more feet deep linked the artillery in the rear with the front trench. On the Somme the British did not capture most of the third line until late September.
‘No man’s land’ between the front lines might be as narrow as five to ten yards or as wide as 1,000, but it averaged 100 to 400 yards. Beyond it, when the Germans attacked, they encountered trench systems less solid and elaborate than their own, though still adequate. The Belgians held the sector stretching fifteen miles inland from the coast, and the British zone ran south of them for twenty to twenty-five miles at the end of 1914 but over 100 by the start of 1917. None the less, until the Americans arrived the French guarded at least three-quarters of the Allied line. In January 1915 Joffre directed his troops to divide their front between ‘active’ and ‘passive’ sectors. Strongpoints in the former would cover the latter, which would be heavily wired but guarded only by sentries. Shellproof shelters behind the strong-points should accommodate counter-attack companies, and a second line would be dug two miles behind. The entire complex should be garrisoned thinly to economize on manpower and save casualties. In the forested Vosges, and even in the tangled woods around Verdun, there were separate blockhouses rather than a continuous defence. The British approach lay somewhere between that of the French and the Germans. Their front was more thickly garrisoned than most of the French one, and they could yield less ground without surrendering their lateral railways or being driven into the sea. Normally they had three parallel positions: the front, support, and reserve lines. The first line was built up with sandbagged breastworks as well as being dug into the earth: in waterlogged areas the ‘trenches’ might be mainly above ground. The first line comprised the fire and the command trenches, some twenty yards apart. In the fire trench small forward units occupied the ‘bays’ between the traverses; the command trench contained strongpoints, dug-outs, and latrines. Communication trenches ran to the support trench, 70 to 100 yards behind, which had more wire and deeper dug-outs; another 4–500 yards back lay the reserve trench, with yet more strongpoints and dug-outs; and behind that, the artillery. In practice the system was far less orderly than laid down in regulations, or than in the mock-up created in Kensington Gardens for the London public. In active sectors trenches were continually blown up by mining and bombardment and the approach to the front became a labyrinth of craters and impasses, to whose complexities newcomers needed seasoned guides.
In their way the trenches were an imposing engineering achievement, the more so if account is taken of the immense infrastructure behind them. It comprised hospitals, barracks, training camps, ammunition dumps, artillery parks, and telephone networks, as well as military roads and canals, but pre-eminently it meant railways. The Western Front lay in one of the most densely tracked parts of Europe, and both sides added hundreds more miles of standard- and narrow-gauge line. In 1914 the Germans took the trunk railway running from Metz to Lille (and onwards east of Ypres towards the sea); the fighting stabilized between it and the main lines running behind the Allied front from Nancy via Paris to Amiens. In the British sector two transverse lines extended northwards from Amiens to Hazebrouck and Dunkirk, and a third, to Arras, was added after the Somme. Both sides pre-positioned support forces near vulnerable portions of their fronts, but the railways enabled larger reinforcements. By day two at Neuve Chapelle the German number of defenders had risen from 4,000 to 20,000; the French ran in 832 reinforcement trains to Verdun in the first three weeks of that battle; and in the first week of the Somme Germany moved up ten divisions in 494 trains. Beyond the railheads both sides depended heavily on horses and ultimately men to convey supplies to their artillery and the front lines, but the railways gave the defender a crucial advantage in funnelling in reinforcements before the attackers could consolidate and expand their footholds.
In addition to the railway network, Western Front defenders benefited from the panoply of innovations ushered in by the nineteenth-century revolution in military technology. In trained hands a breech-loading magazine rifle could fire up to fifteen rounds a minute, at a range of half a mile. Using smokeless powder and firing in a prone position, riflemen were almost invisible, and the kinetic energy of a rotating high-velocity bullet gave it an impact against bones and tissue out of all proportion to its size. But machine-guns and field artillery were the mass killers. European armies all had versions of the Maxim gun, and were equipped with light as well as heavy machine-guns as the war progressed. A heavy machine-gun typically weighed 40–60kg, even without its carriage and ammunition belts, and needed three to six men to operate it; light machine-guns (such as the British Lewis gun and the German MG 08/15) weighed 9–14kg, and were more suitable as offensive weapons, as a man could – with difficulty – carry one. In August 1914 a standard German infantry regiment comprised twelve companies of riflemen and only one of machine-gunners (with six weapons), but in 1915 six more machine-guns were added and in 1916 the same again, raising the proportion of machine-guns to rifles from 1:12 to 1:4. By 1917 the ratio in many divisions was 1:2. One heavy machine-gun could fire up to sixty rounds a minute, equivalent to as many as forty riflemen. Its range was greater, and it could ‘beat’ (i.e., fill with flying lead) an ellipse 2,500 yards long and 500 yards wide. As long as its attendants fed in belts of bullets and topped it up with cooling fluid it could continue its lethal traverses, one at Loos firing 12,500 rounds in an afternoon. At Neuve Chapelle two machine-gun posts held up the British until reinforcements arrived; and two guns halted the French at Neuville St-Vaast on the first day of the May 1915 attack. On the second day at Loos German machine-gunners inflicted thousands of casualties on novice BEF divisions for almost no loss to themselves. On 1 July 1916, however, many British casualties were caused by artillery rather than machine-guns. Both sides kept field guns targeted on no man’s land and the opposing first line so that they could respond at once with ‘SOS fire’ if the sentries sent up flares. By September 1915 in Champagne the Germans had perfected the art of siting their field guns on ‘reverse slopes’, so that as the Allies came over a crest and advanced downhill they were in full view from the German artillery, which the slope had kept invisible from the Allied gunners. At Verdun French artillery west of the Meuse disrupted Falkenhayn’s attack plan, while on the Chemin des Dames German guns wreaked havoc on Nivelle’s tanks. In this period of the war the combination of trenches, railways, rifles, machine-guns, and artillery was too strong for attacking forces to overwhelm.
The principal weapon available to the attackers was bombardment. Both GHQ and GQG altered their tactical doctrine during 1915 to stress its vital role in destroying enemy positions before the infantry could occupy them. It has been calculated that shellfire caused 58 per cent of the war’s military dead. Yet the artillery was a blunt instrument. The quick-firing field gun’s flat trajectory made it of little use against entrenchments, especially as in 1914 most field gun shells were not high explosive but shrapnel, scattering fragments that mowed down infantry in the open but lacked the blast effect needed against earthworks. In any case the Allies were short of shells of any description by the first winter of the war. For precisely such reasons the Germans could protect themselves against the French 75mm cannon by digging in. Moreover, French divisions were not equipped like German ones with light field howitzers (whose curved trajectory was much more appropriate against trenches), the whole army possessing only seventy-eight 105mm howitzers in June 1915. Their stock of heavy artillery was small, outdated, and kept under GQG’s central control. Matters did improve. In Champagne in September 1915 the French attacked with 1,100 heavy guns, compared with 400 in Artois in May, and after a bombardment lasting not four hours but several days. Similarly, before the Somme the British had in total more than twice as many guns as at Loos, and four times the number of howitzers. But it was still not enough, and not simply because the German defences grew ever more sophisticated. High explosive shells needed a heavy metal casing to stop them disintegrating: the explosives themselves accounted for only 900 tons of the 12,000 tons of munitions fired before the Somme. Even so, many shells failed to detonate or did so in their own guns. Also, artillery fire was highly inaccurate. In the open campaigning of 1914, guns could operate as in previous wars by ‘direct fire’: the crew could see their target and fire ranging shots until they hit it. But in such conditions they too might be visible, and on the quick-firing battlefield visibility was hazardous. In trench warfare ‘indirect fire’ from a concealed position against an invisible target became the norm. In a procedure known as ‘registering’ the gunners adjusted the range, barrel elevation, and explosive charge on advice from a forward observation officer (FOO), ideally telephoning from the front line, or from an observer in an aircraft reporting by wireless. Registering was slow and gave the enemy warning, while the FOO might be blinded by rain or smoke or his telephone line might be severed (and in a battle it often was, making communication dependent on carrier pigeons or runners). The Germans could tap into British telephone conversations within a one-mile radius, though in 1915–16 the British developed more secure communication methods such as the ‘Fullerphone’ and the ‘power buzzer’. Even when a gun had found its target, varying wind speeds and atmospheric temperatures and pressures could alter the fall of the shell, as could wear and tear to the barrel. For all these reasons, artillery preparation repeatedly yielded disappointing results. On the first day at Verdun an unprecedentedly intense German bombardment failed to annihilate a sketchy but cleverly dispersed French defence. When the assault troops advanced they came under heavy fire. On the Somme the British fired over 1.5 million shells in five days but on most of the front neither cut the Germans’ wire, nor smashed their dug-outs, nor silenced their guns. British commanders operated by guesswork and failed to calculate (in fact grossly underestimated) the bombardment needed to destroy the enemy front line. They arrived at the correct formula almost by accident at Neuve Chapelle, where they stealthily concentrated almost all the BEF’s artillery against a single-line defence, but they did not match this density of shells until Arras two years later. Such quantities were needed against just the first position, however, that it was not feasible to destroy the entire depth of enemy trenches, and by attempting to do so Haig on the Somme and Nivelle on the Chemin des Dames ensured their artillery would be ineffective. Moreover, as the Somme battle developed the Germans left their trenches during barrage and dispersed into the surrounding shellholes, creating such an extended target that no bombardment could destroy it. Enlarging and prolonging the bombardment in the hope of blasting through a passage by weight of explosive and metal was a fruitless quest.
Reliance on artillery preparation also contributed to tactical inflexibility, and made surprise virtually unattainable. Preparing a Western Front offensive was akin to a major civil engineering project. The British used 21,000 black South Africans in labour battalions in Europe: by the end of the war they made up 25 per cent of the labour force on the Western Front.
The French imported labourers from China and Vietnam. But the soldiers themselves did most of the work, and an integral part of the trench experience was hard and unremitting manual effort. Preparations on the Somme began in December 1915 in a poorly accessible region that lacked housing, roads, and railways, and even surface water because of the chalky terrain. By July 1916 the British had dumped forward 2.96 million artillery rounds, laid 70,000 miles of telephone cable (7,000 at a depth of more than six feet), and built fifty-five miles of standard gauge railway for a battle expected to require 128 trains a day. The French were at work for two months before the September 1915 offensive and the April 1917 attack – though in the latter case they needed more time than Nivelle’s impatience allowed them because the proposed location’s drawbacks included very poor transport links. Among the reasons why Falkenhayn persisted at Verdun, Haig on the Somme, and Nivelle on the Chemin des Dames was the scale of the preliminary investment in each battleground and the delay and expense entailed in preparing fresh attacks elsewhere.
Given the limitations of heavy artillery it was unsurprising that both sides sought alternative solutions, mobilizing their scientific and industrial communities for the purpose. To begin with the Germans were not only better trained and equipped than their opponents for trench construction but also better provided with assault weapons. Hand grenades were standard issue in the German army in 1914, as were light mortars. The Mills bomb, which became the main British grenade, caused many accidents when first introduced, and only in 1916 did a safer version follow. The Stokes mortar, designed at private initiative and ordered by Lloyd George as minister of munitions, was similarly in general service only from 1916. The Germans also introduced the flamethrower, first employed on the Western Front in February 1915. Virtually all the flamethrowers in the German army were brought to bear against the fortresses and blockhouses at Verdun, but they were used less frequently in the later stages of the battle as they had only a short range and their operators presented easy targets. The British on the Somme also employed flamethrowers, but despite the horrific injuries and panic they could generate, they were more spectacular than effective. All these weapons, however, were more suited to raids or to clearing enemy trenches than helping troops cross no man’s land in an offensive. Three other technologies promised more in this latter respect. The first was tunnelling under the enemy trenches to lay mines, which began in the winter of 1914–15 and was mainly a feature of the Anglo-German front. Mines were exploded on the first day of the Somme, although by being detonated ten minutes before zero hour they gave warning of the assault. Mining was an even slower and a more hazardous activity than preparation with heavy artillery, though if kept secret it could bring the benefit of surprise. It was unsuited, however, to be more than a supplementary attacking device.
The remaining two developments – poison gas and tanks – were much more important in the course of the war. Both were designed to overcome the trench stalemate. The British had experimented with gas before the war and the French fired projectiles from rifles and may have used gas grenades in the winter of 1914–15, but the substances concerned were irritant rather than lethal. Although there are plausible grounds for saying the Allies would have used gas if Germany had not, the Germans are rightly saddled with the opprobrium attached to introducing it, which was to be one of the war crime charges levelled against them at the peace conference. After trying out tear gas against the Russians, on the afternoon of 22 April 1915 they commenced the second battle of Ypres by releasing the cloud of chlorine that began the massive chemical warfare that distinguished the First World War from preceding and from most subsequent armed conflicts. In all, 124,208 tons of gas were used during the war, half of this quantity by Germany. The quantity quadrupled from 1915 to 1916, doubled in 1917, and doubled again in 1918. By 1918 the technology employed about 75,000 civilians in large and dangerous manufacturing operations, as well as thousands of specialized troops. It claimed perhaps half a million casualties on the Western Front (including 25,000 fatalities), in addition to 10,000 in Italy and a large but unrecorded number in Russia. But gas warfare was a microcosm of the conflict as a whole in its combination of escalation with stalemate. The best chance of its becoming a breakthrough technology was when it was first used, but if a moment of opportunity existed here, it was, as usual, lost.
Germany much exceeded Britain and France in its manufacturing and research capacity in chemicals and until the end of the war it mass-produced toxic gases faster and more efficiently. Falkenhayn saw gas as a tactical tool that might facilitate the decisive result he craved in the west and compensate for shortages of shells. The Germans satisfied themselves that they could reconcile their actions with a pedantic reading of the 1899 Hague Convention, and Falkenhayn’s technical adviser, Fritz Haber, told him early retaliation was unlikely. Most of the army commanders were hostile, fearing that if the Allies did reciprocate Germany would be disadvantaged by the prevailing westerly winds over France and Flanders. The commander in the Ypres salient was willing to try, but it became evident that gas had major shortcomings. To save shells it was decided to deliver the chlorine from almost 6,000 pre-positioned cylinders, which were bulky to transport and difficult to conceal (although the Allies ignored the intelligence warnings), as well as being liable to leak and therefore extremely unpopular with the troops. Success depended on a favourable wind, which took weeks to materialize. OHL therefore did not expect spectacular results, but envisaged a limited operation that would disrupt the Allies’ spring offensives, distract attention from Germany’s troop movements to Russia, and (by capturing Pilckem Ridge), make the Ypres salient indefensible. In the event, when the gas cloud was released at 5 p.m. against Algerians who mostly panicked and fled it opened an 8,000-yard-wide breach north of Ypres, but the Germans had few reserves on hand and the troops they sent forward had no masks. The Allies used the night to close the gap, and a second release, against Canadians two days later, had less impact. By June primitive respirators had been issued en masse to the Allied armies, and in September the French used gas in Champagne and the British at Loos. Haig had high hopes for it and was confident it would enable him to break the German line despite his continuing shortage of shells, but on the morning of the attack at Loos the air was still and although the chlorine cloud helped in some sectors it gassed more of his own men than the enemy.
After Loos there was little likelihood or expectation on either side that gas would be a war-winning weapon, although both continued to use it (the Germans against the Russians during the summer campaign in Poland in 1915 and on the Western Front a dozen times more down to August 1916). On balance it aided attack over defence. Although both sides introduced better respirators (notably the British Small Box Respirator or SBR) they also introduced more poisonous gases and new methods of delivering them. Phosgene, six times more toxic than chlorine, was brought in by the French at Verdun, fired in shells and therefore less dependent on the wind; the Germans used diophosgene or ‘Green Cross’ shells before their culminating attack there on 23 June (though they ended the bombardment too soon and French masks were reasonably effective against it). On the first day at Arras the British fired great quantities of phosgene from a new mortar-like device, the Livens projector. The projector was much easier to set up than the cylinders had been, and the Germans greatly feared it because it gave almost no warning. In general the Allies were gaining the edge in the gas war until in July 1917 the Germans attacked the British with mustard gas, opening a major new phase. Although both sides pointed out, with some justice, that gas caused less terrible injuries and fewer fatalities than did high explosive, it continued to evoke peculiar horror, and made conditions for the front-line soldiers even more difficult. Once the gas shell replaced the cylinders its use became much more widespread. Yet it remained an ancillary, harassing weapon that at Second Ypres, Verdun, and Arras facilitated temporary successes but produced no radical results.