In truth, the subject of a Belgian offensive had been widely mooted in Whitehall since the close of 1916 and had periodically resurfaced in conversations with GHQ ever since. Work to improve the transportation links between the northern ports and Flanders had even been ordered in December 1916, presumably to support any future offensive in the region. But Lloyd George preferred to look the other way, interpreting the meeting in Paris as being in line with his strategic vision, and assuming that he would always be able to control his generals. The problem was that Haig did not see it this way. From his perspective, the Prime Minister had authorized his commanders to get on with things as they saw fit, and this was exactly what they were doing. Because Haig was not someone who would dawdle or play for time; he was, on the contrary, a man in a hurry.²²

Lloyd George’s interpretation of events may have been questionable, but Haig had an equally tough job persuading his chief allies that his plan was sensible. It had been assumed throughout that the French would play some part in the attack, even if just mounting operations to draw off German reserves (as had been agreed at Paris several days earlier). Yet over the coming weeks this assumption gradually fell away. As outbreaks of mutinies and indiscipline began to spread, rumours reached GHQ that something was very wrong in the French Army. When Haig met Pétain on 18 May, he asked him bluntly:

‘Did the French intend to play their full part as promised at the Paris Conference? Could I rely on his whole-hearted co-operation?’

Nodding slowly, the French Commander-in-Chief gave Haig his full assurances that the French would continue to attack. He was planning, he said, four minor operations, including one scheduled to take place at La Malmaison, on the Chemin des Dames, on 10 June. He had also agreed to send six divisions, under General Paul Anthoine, to Flanders to cooperate on the left of Haig’s forces.²³

Pétain did, however, express a murmur of concern. He was afraid that Haig would repeat the mistakes of General Nivelle. The objectives for the ‘northern offensive’ were too deep, too far into the German line, too ambitious. He suggested that they should be shorter and more limited, although, of course, that was up to the British Commander-in-Chief to decide.²⁴ It was a warning though: a clear call to rethink some aspects of Haig’s plan; to look again at the viability of a major breakthrough and to learn lessons from Nivelle’s failure. It was a warning that Haig would have been well advised to heed. But, fossilized in his own certainties, he took no notice of it. He had confidence in his own army, because, after all, his men were improving their effectiveness all the time, as shown in their recent operations at Arras, where British and Dominion forces had supported Nivelle’s main thrust with a series of powerful preliminary attacks. Moreover, their morale remained high and they were showing little or no signs of the indiscipline that was eating away at the French. For Haig, Pétain was a pessimist, and pessimists never won wars.

Much of Haig’s confidence about what could be achieved for the remainder of the year stemmed from his profound faith in the ability of the men he commanded. By May 1917 the BEF was approaching its peak; it was split into five armies, which held the front from Boesinghe, in Flanders, down to the city of Saint-Quentin, in the rolling hills of Picardy. With over 1.8 million men under arms and supported by an impressive array of weaponry and equipment, it was, by some considerable margin, the most powerful army Britain had ever raised.²⁵ The original expeditionary force had been manned by long-service regulars–the legendary ‘old contemptibles’–who could fire twenty-five aimed rounds per minute and put the fear of God into the German Army at Mons in 1914. Yet three years later, most of them had gone: either killed or invalided home; their ranks thinned on the murderous fields of Ypres and Aubers Ridge, Loos and the Somme.

The loss of most of Britain’s regular soldiers meant that the Army of 1917 would be a radically different organization. The ranks of the BEF had initially been bolstered by a combination of territorials and reservists, before the legions of Kitchener’s volunteers–those who had joined the colours after the outbreak of war–began deploying to France from the summer of 1915. However, the continuing expansion of the Army, combined with heavy losses at the front, meant that the British Government had to resort to more direct methods to keep up the strength of Britain’s forces. On 27 January 1916 the Military Service Act became law. This ordered the conscription of single men between eighteen and forty-one (exempting conscientious objectors or those unfit) and was followed four months later by the second Military Service Act, which extended its provisions to include all men, married or single. Thus, the Army that fought at Third Ypres was closer to being a ‘nation in arms’ than at almost any point in Britain’s history.²⁶

Haig’s army reflected the nature of the society it came from: solid, dependable, patriotic, but also light-hearted with a self-deprecating sense of humour. Perhaps it was not as effective or as glamorous as other armies, it had a certain stuffiness to it that contemporaries noted, and many of its key positions were still held by old regulars who had never been entirely happy with the rapid expansion of the Army in 1914 and 1915. Yet it was difficult to beat, tenacious and determined in defence, and increasingly effective in attack–and it brought with it the tremendous industrial and economic power of the British Empire, which was then reaching its zenith. Hundreds of thousands of men from the great Dominions of the empire would come to the Western Front during the war: Canadians, Australians, New Zealanders and South Africans; and all would find themselves drawn to the Flanders battlefield in that fateful summer of 1917.

Fighting at Arras continued, fitfully and in gradually worsening conditions, until 17 May, when operations were finally brought to a halt. The battle may have opened with great success on 9 April, but the last operations had a familiar, Somme-like quality with poor ground conditions and murderous trench warfare that consumed divisions at an alarming rate. At Bullecourt, a nondescript and by now ruined village southeast of Arras, two brutal battles were fought as British and Australian troops tried to push forward against sections of the heavily defended Hindenburg Line. In charge of the operation was General Sir Hubert Gough–the man who would make the main assault at Ypres–and Bullecourt would offer his critics further proof, if any were needed, of his aggression and stubbornness. After two weeks of heavy fighting, the village of Bullecourt was evacuated by the enemy, but it hardly felt like a victory. In this one sector alone, the BEF had sustained 14,000 casualties, with the dead lying in clumps on the battlefield.²⁷

Gradually, as operations at Arras were shut down, British battalions began their move to Ypres. In the warm spring air, units marched, or were bussed, to their new billets, swapping the undulating uplands of the Somme or the coke-smeared industrial zone of Lens, for the flat, ominous landscape of Flanders. Undoubtedly the Somme could be beautiful at times, particularly in the summer when the air buzzed with skylarks, but Flanders–the ‘wet Flanders plain’, as the novelist Henry Williamson put it–was always a dreary, shell-plastered wasteland and Ypres, its capital, was always a city of the dead.²⁸ By 1917 ‘Wipers’, as the British called it (being chronically unable to get the Belgian pronunciation correct), had become a byword for the perils of trench warfare. On other sectors Tommies could look forward to months of ‘live and let live’, enjoying regular periods of peace and quiet, and perhaps organizing a series of mutually beneficial ‘arrangements’ with the enemy, but this was never the case at Ypres. Troops coming into the line knew they were entering a perilous place where shelling and sniping were constant dangers–made even worse by the grandstand view the enemy had of all your movements. ‘Here “Fritz” was right on top of you.’²⁹

Few soldiers looked forward to going there. Lance Corporal H. S. Taylor, an NCO with the Liverpool Scottish (1/10th King’s Liverpool Regiment), remembered coming into Ypres that spring, travelling from Poperinge in a small passenger train that was shunted up in the darkness. The mood among the men was phlegmatic and depressed at the prospect of going into the Salient, knowledge that was evidently too much for one of his platoon–a young private who ‘shattered the index finger of his right hand with a bullet from his own rifle’ during the journey. From the station they took what would become a familiar rite of passage: marching through the ruins of Ypres before taking their positions at the front. The worst part, according to Taylor, was traversing the large expanse of the Grande Place, feeling ‘very exposed’ as they sidled past what remained of the Cloth Hall. It was ‘an eerie experience for me, and I have no doubt many others’, he wrote, ‘as it was frequently shelled at night with shrapnel and high explosive. One felt an irresistible urge to hurry into the nearest side street where there might be a little shelter. Shell-holes were endlessly being filled in… for the benefit of the night transport.’³⁰

While Ypres would remain the focus for the remaining months of the summer and autumn, for the time being the Messines Ridge took centre stage. Plumer’s attack would illustrate many of the developments that were transforming the BEF’s way of war. As had been seen on 9 April, the British were rapidly evolving a tactical system that could break into almost any position on the Western Front, and do so at an acceptable cost. The problem was that infantry on their own could not cross no-man’s-land–that blasted wasteland between the opposing sides–without exposing themselves to heavy gunfire, from rifles and machine-guns, that could shatter the cohesion of the attacking waves. They were also extremely vulnerable to pre-planned enemy barrages that were zeroed in on no-man’s-land and came down within minutes of an assault, thus preventing any supports or reserves from coming up. Even if they were able to close with the enemy trenches, the attacking waves would then run into rows of barbed wire that funnelled them into killing zones or stopped their progress dead. The battles of 1915–16, the barren years of suffering and trial and error, were littered with episodes that made survivors shudder: of rows of corpses in no-man’s-land; of entire companies ‘hanging on the barbed wire’; of great hopes lying shattered in the mud.

Artillery fire seemed to offer the obvious solution to the dilemma of trench warfare. If enough shellfire was concentrated on the right target, then it could cut barbed wire, neutralize the defending garrison (at least temporarily), and destroy enemy batteries. The problem, however, lay in the detail: in getting the artillery to hit the correct target at the right time (and with a suitable weight of shellfire). In earlier years, British guns had simply not been up to the job. They were frequently inaccurate. Their shells were often unstable, meaning that a considerable proportion failed to explode (perhaps as many as a third on the Somme).³¹ Even the type of shell mattered as tests showed that shrapnel–the most widely available munition–was frequently ineffective against thick wire entanglements, with many units preferring high explosive (which was only available in limited quantities). In addition, it was always difficult to locate enemy gun batteries. They moved regularly and were usually hidden behind ridges or woods and, in any case, offered only a very small target.

The solution to all of this took years to develop and perfect. After the ‘shells scandal’ of 1915–when shortages of vital munitions had caused a grave political crisis–a Ministry of Munitions had been formed that was instrumental in energizing British industrial production. Although it took some time for new factories to be built and become operational, by 1917 the effects of this revolution were being felt. The BEF now had access to many more guns (including the vital ‘heavies’) and shells were being produced in almost unlimited quantities (and were generally much more reliable). Pioneering efforts were also being made to locate enemy batteries through the techniques of ‘sound ranging’ and ‘flash spotting’. Essentially, this entailed recording the sound waves of passing shells through a series of microphones, and then working out where they came from. Observers were also tasked with watching out for the muzzle flash of enemy guns and locating their position through a process of triangulation.³² Moreover, by the time the British fought at Arras, there had been a ‘huge increase’ in the technical skills of the Royal Artillery. Gunnery officers were now making much more effort to fire accurately, by taking measurements of the wind and air pressure, and the effects of shell weight and propellant, and then adjusting the range and bearing accordingly. This was a long way from the approach of 1914, which had been based on guesswork: open fire, see where the shell landed, and then adjust.³³

Yet being able to deluge targets with sustained and accurate shellfire was only one element of the Army’s increasingly combined approach. The Royal Flying Corps took on a growing role in artillery spotting and ‘contact patrols’ throughout the war. Aircraft ranged over the lines photographing or bombing targets and attacking enemy aircraft. But this was never easy. In the spring of 1917 the RFC had faced its toughest test in the skies above Arras. In what become known as ‘Bloody April’, the British struggled to deal with superior German aircraft (such as the Albatros D.I, D.II and D.III) that were faster and able to outclimb their machines. Organized into Jastas, and led by elite pilots such as Baron Manfred von Richthofen, the German air force enjoyed a period of remarkable success.³⁴ In April alone, 275 British aircraft were shot down, causing the death of over 200 pilots and observers. It was even estimated that many of those who died had barely 100 hours’ flying time before they came under the guns of Germany’s elite fighter squadrons.³⁵

The answer to the ‘Red Baron’ and his ilk was, as with the artillery, partly technological, partly tactical. The RFC had to get on with the job of supporting the ground forces as best it could while waiting, impatiently, for a new generation of aircraft to roll out of the factories. By early summer, however, things were beginning to turn in their favour. New aircraft, including the SE5 and Sopwith Camel, were arriving in France in significant numbers and helped the British re-establish their edge in the air. The SE5 was first introduced to the elite 56 Squadron in April 1917 and, although initially experiencing some teething problems, it went on to become one of the most famous aircraft of the war: fast, able to climb quickly and safely, and a match for all German fighters. Captain James McCudden, a pilot with 56 Squadron, called the SE5 ‘a most efficient fighting machine, far and away superior to the enemy machines of the period’, which was also ‘almost warm, comfortable [and] an easy machine to fly’.³⁶ Together with the Sopwith Camel, which would become the most successful Allied fighter of the war, the British had the aircraft to secure control of the air above the Western Front by the summer of 1917.³⁷

Artillery and aircraft were not the only weapons transforming the nature of war. Eight months earlier, in the charnel house of the Somme, Britain had pioneered the use of armoured vehicles, known as tanks. By the time of Messines, the original Mark I had undergone considerable modification, and the latest variant, the Mark IV, was now arriving in France. It was a considerable improvement on its predecessor, with thicker armour (to protect against German armour-piercing bullets) and better internal mechanics (an armoured petrol tank and a more reliable fuel delivery system) that resulted in improved performance on the battlefield and prompted, in the German Army, a growing scramble for adequate counter-measures. Although the tank clearly remained a weapon of the future, and mechanical reliability was always an enduring challenge, it was another indication of just how hard the British were working to break the trench deadlock.³⁸

In all this, the infantry–the lone man among the chaos–was not forgotten. Platoons were now being equipped with a variety of weapons that would enable them to fight their own way forward if necessary. As well as the rifle and bayonet, British soldiers now had access to the Mills bomb (a reliable time-fused grenade); rifle grenades (which attached to a special cup fitted to the muzzle of a rifle); the Lewis gun (a semi-portable light machine-gun); and, from March 1917, the 3-inch Stokes mortar (which provided a short-range deluge of fire, either high-explosive or smoke). With these weapons it was now much easier for British infantry to take on German strongpoints or deal with counter-attacks. When combined with new tactics that emphasized ‘fire and movement’, with flank attacks and infiltration being employed to help them get across that ‘fire swept’ zone, British infantry now had a much better chance of surviving on the battlefield than they had the previous year.³⁹

Despite the tactical and technological sophistication with which the BEF now approached battle, considerable hurdles still remained to be cleared. Breaking into an enemy position could be achieved with a degree of certainty (particularly when compared with a year earlier), but serious questions were being asked about how far troops should go, and whether any large-scale breakthrough could ever be achieved. With the failure of Nivelle’s offensive, Pétain realigned the French Army towards the worship of heavy shellfire and slow, sure advances (so-called ‘Pétain tactics’), but the British never came to such a clear epiphany. Haig, for one, was never entirely happy with the French Commander-in-Chief and was always convinced that a breakthrough could be achieved, even if growing numbers of his subordinates, including numerous senior corps and army commanders, were much less sanguine about the prospects for such a climactic attack. This friction between limited and unlimited attacks would run through the entire history of the BEF on the Western Front.⁴⁰

Sir Henry Rawlinson, Fourth Army commander (and the man whom Haig had put in charge of a possible amphibious landing), was the leading advocate of so-called ‘bite-and-hold’ attacks. Echoing Pétain’s conclusions about renouncing large-scale offensives aiming to drive deep into the German line, Rawlinson felt the Army should fight in an avowedly attritional manner. Utilizing as much firepower as possible, they should conduct limited, ‘step-by-step’ operations to seize local points of tactical importance, ideally on high ground. Once these had been ‘bitten off’, the enemy would be compelled to counter-attack at a disadvantage, allowing the British to bring their artillery to bear and cause the enemy heavy losses. As early as 8 February 1915, Rawlinson had written that ‘If the Germans are to be defeated they must be beaten by a process of slow attrition, by a slow and gradual advance on our part, each step being prepared by a predominant artillery fire and great expenditure of ammunition.’⁴¹ Although at that time the amount of firepower required was simply not available, as an operational concept it was a revelation. The only problem was that Haig remained unconvinced. For him, ‘bite and hold’ could be no more than a temporary, limited response to conditions in the field. The breakthrough and the decisive offensive would always remain an article of faith and the essence of campaigning.

Notwithstanding Haig’s natural aversion to ‘bite and hold’, the opening of the Arras offensive began with a series of well-planned, limited attacks. Because of the nature of the ground, and the absolute necessity of securing the Messines Ridge, Plumer would be allowed to do the same: to concentrate his combat power on a clear, definitive objective without going for an ‘all-out’ success.⁴² At Messines, the infantry and artillery would be coordinated into a set-piece attack that was timed to perfection. Firstly, Plumer’s mines would be blown, hopefully fatally weakening the German defence and allowing the infantry to seize their objectives. In the weeks preceding the attack, they were specially trained for the assault. Plumer wanted every man to know as much about his objectives as possible, so large-scale models and training grounds were constructed that allowed the troops of each battalion to familiarize themselves with their objectives and conduct exercises over them. Even if their officers became casualties, through the smoke and fire, the British soldier should still know what to do.⁴³

The attacking infantry would be supported by one of the most elaborate displays of firepower in the history of war. An eleven-day bombardment would soften up the defences along 17,000 yards of front, with Plumer’s guns eventually hurling a total of 3.5 million shells into the German positions. Following the explosion of the mines, all of Second Army’s artillery–over 2,000 barrels–would open fire simultaneously at Zero Hour, forming three lines of barrage fire that would obliterate what was left of the German front line. At the same time, heavier batteries would deluge all known enemy gun positions with concentrated shellfire, aiming to prevent any possible retaliation. As if that were not enough, Plumer also managed to get his hands on seventy-two Mark IV tanks, which would be parcelled out across the front and used against specially selected strongpoints, where their thick armour and 6-pounder guns would prove very useful should the advance be held up. As far as preparations went, it was remarkably impressive. Plumer–more than any other British commander on the Western Front–vowed to leave nothing to chance.⁴⁴

Time was now of the utmost importance. Nivelle’s operation had backfired spectacularly, but there were still enough months in the remainder of the campaigning season for one more major effort. Morale in Second Army headquarters at Cassel was excellent. Haig visited Plumer on 22 May and found him ‘in very good spirits now that his Second Army occupies the first place in our thoughts!’⁴⁵ According to Plumer’s Chief of Staff, Tim Harington, when they received the go-ahead from GHQ, they became ‘full of hope’. ‘The Second Army had its chance at last. We were going to be tried out. It was a wonderful month. Everything we wanted we were given.’⁴⁶ As they were speaking, the final elements of Plumer’s plan were clicking into place: the artillery bombardment had already begun softening up the enemy defences, while the assault troops were going over their final deployment orders. In the half-light of dawn on 7 June, the attack on Messines Ridge began. It would be the first part of Haig’s long-awaited Flanders campaign.