The main British mining operation of 1915 was that at Hill 60 and has already been described. Other than this, no great effort was made to coordinate the mining operations with any military initiative; even the mines detonated at the onset of the Battle of the Somme in mid-1916 had little impact on the outcome of the ensuing prolonged bloodbath. Mining remained localised and consisted of recurring episodes of tit-for-tat mining and counter mining with the British as they gained in experience and organisation slowly nullifying the initial German advantage.
At the end of 1915 some 20 tunnelling companies each comprising up to 1,000 men and ever increasing quantities of equipment had been formed. Losses were high; almost 1,000 men were killed, wounded or ill each month and had to be replaced. In addition, apart from tangled networks of galleries around the trenches, some enemy casualties and shaken German morale, there was little to show for this considerable effort.
However, improvements were on the way. On 1 January 1916 Brigadier General R N Harvey was appointed inspector of mines with overall control over the tunnelling companies and the integration of their work into the war effort at as a strategic as well as a tactical level. It all culminated in the greatest feat in destructive military mining the world had ever witnessed at Messines Ridge on 7 July 1917 as the prelude to the successful assault there.
THE YPRES SALIENT
The geology of the Messines Ridge is straightforward, a succession of horizontal clay and sand layers of the Paniselian Formation overlying the Ypres clay that forms much of the Flanders plain. The ridge has a covering of Quaternary sand that reaches a thickness of some 30m to the south of Kruisstraat.
The struggle here was determined by topography and geology. The Germans held the advantage above ground overlooking the British positions to their west from the high ground of the Messines Ridge. A north-trending spur of the main Passchendaele Ridge. On the other hand the British had easier access to the Ypres blue clay and the sandy clay and the clay layers of the Paniselian Formation on top of it. Like its London clay counterpart the Ypres blue clay is stiff, overconsolidated and prone to swell when exposed to moisture; it is eminently suitable for tunnelling. Above those lie the Kemmel Sands which were an almost impassable obstacle to mining. Up to 10m thick along the Ridge this layer of fine sands was full of water trapped between the moist or dry clays below and a seam of moist sandy clays above; the result was a layer of quicksand aptly known to the German miners as ‘schwimmsand', meaning swimming sand. All attempts to drive tunnels at depth beneath the Ridge were bound to intercept this saturated layer unless their entrances were located in the low ground to the west behind the British lines or in the valley of the River Douve.
The impasse of the Kemmel Sands was overcome in May 1915 at Cuinchy where a 1.8m diameter spiled timber shaft was sunk through 2m of running sand into the dry clay underneath by a section of 170 TC under Lieutenant J A Leeming. He was immediately instructed by Major Norton- Griffiths to seal the shaft with a cylindrical iron lining; a supply of specially designed steel tubbing, initially fabricated in France and later in Britain was obtained. Such steel linings, typically 1.8m in diameter, were to become the key to shaft sinking through the waterlogged sand layers into the stiffer and drier clays underneath. They were easy, quick and safe to install; if great thickness of saturated sand had to be penetrated two or three diameters of tubbing could be used with the size of the shaft decreasing with depth. As soon as the tubbing was embedded in the clays the shaft was continued with timbering.
When the required depth had been achieved tunnelling began with galleries being driven towards the enemy positions by the clay-kickers. Again, support was crucial to maintain stability. Invariably tunnels in clay in Flanders were close timbered. This involved the construction of a continuous enclosure of wooden boarding supporting the roof, sides and floor inside which the miners worked. The tunnel was advanced in nine to 12 inch (230 – 300mm) increments by carefully and as silently as possible excavating the ground ahead to the exact shape so that the next timber sett could be inserted. Nine by three inch (225 by 75mm) hardwood planks for strength and durability with stepped joints were commonly used as support. By the middle of 1916 the British had standardised the internal dimensions of their workings; ordinary offensive and defensive tunnels were 1.3m by 0.69m increasing to 1.5m by 0.76m near the shaft bottom while communication tunnels were 1.83m by 0.9m.
These dimensions were chosen to maximise progress but were certainly cramped. Infantry detailed to assist the miners particularly disliked that chore. Conditions were uncomfortable, dim and generally stuffy; water often dribbled into shallow tunnels. Although rarely encountered there could be problems with ventilation and with lack of oxygen and with the increased pressures on the timber support in the deeper tunnels. But above all this, the perpetual game of cat and mouse, kill or be killed, pervaded the atmosphere. It was psychologically disturbing and nerve-wracking for the tunnellers, officers and men; and only alleviated by liberal supplies of rum.
THE BIG IDEA
The Big Idea was sown in Norton- Griffiths' mind in spring 1915 as he stood in the rain gazing across noman's- land at the German front line along the Ypres Salient with Wytschaete and Messiness further behind. Mulling it over and examining trench maps he became convinced that six large deep mines placed strategically should be capable of blowing the Germans off the Messines Ridge. He sent the idea to Colonel R N Harvey but it was reject out of hand by Brigadier General Fowke, engineer-in-chief. But Harvey was persistent and ultimately won Fowke around to the idea.
In November 1915 newly formed 250th TC was settling down to an ambitious mining programme under the command of Captain Cecil Cropper, a metal mining engineer from Northumberland. Positioned opposite Wytschaete and strongly supported by Canadian chief engineer Brigadier General Charles Armstrong Cropper was planning a tunnel attack on the ridge from shafts located well to the rear of the British front line where the blue clay was almost at ground level. Quite independently of Norton-Griffiths and Harvey he had also thought of the Big Idea and was rather upset at their take over of what he considered his idea. Great minds think alike, but only the first to be noticed gets the prize.
And luck was again with the Norton-Griffiths, Harvey and Fowke team when all three of them were summoned to a conference of top generals in January 1916 and asked to submit their plan. Norton-Griffiths did the presentation telling them the plan would save the lives of 10,000 British soldiers in the assault Then after shorter contributions from Fowke and Harvey the plan was for a second time rejected out of hand. But late that same night they learned that the decision had been reversed; the Somme Offensive was planned for the coming July and the generals considered that an 'earthquake' at Messines Ridge further north would be an ideal diversion. There was just six months to get it all ready.
But parts of the plan were already being implemented unintentionally by Cropper as outlined above and by 175 TC under major S H Cowan, already blooded at Hooge, who had started work late in August 1915 on a two-pronged gallery targeting Hill 60 and Caterpillar. Here they had succeeded in reaching the blue clay by laboriously driving a timbered incline through the unstable overlying saturated strata. The gallery driven from it at a depth of 28m was known as the Berlin tunnel.
Throughout the spring of 1916 Field Marshall Sir Douglas Haig, Commander in Chief, continued to plan for a double attack in the summer – an initial attack through Flanders to be followed by an Anglo-French offensive at the Somme. So the tunnelling effort continued along the Messines Ridge where orders were issued mid-February to be ready for action by mid-June.
The longest and most important of the tunnels was at Petit Bois and was least likely to meet the deadline if clay-kicking was used. In an effort to speed up progress instructions were issued to press the excavation well ahead of the timbering; progress rates shot up only for disaster to strike after three days when 13m of tunnel collapsed and the new method had to be abandoned. Simultaneously, Norton- Griffiths was involved in the procurement of a 2.4m diameter tunnelling machine, the Stanley Heading Machine manufactured in Nuneaton and originally designed for use in coal mines. After many misadventures in transit and during assembly on site this machine commenced boring on 4 March. It advanced at about 0.6m per hour for several hours; however, when the machine was stopped it stuck fast in the swelling clay and had to be dug free. The problems multiplied; the electric motor driving the compressor failed; it repeatedly became stuck and had to be freed; the machine tended to dive. By the time the machine had laboriously dug about 60m of tunnel enough was enough and the machine was abandoned and never retrieved.
At Hill 60 the Berlin Tunnel was in a poor state as result of the combined effects of seeping water and nearby mining, shelling and trenching. When early in April the third Canadian TC took over from 175 TC, their inheritance included some 60m of collapse tunnel the result of a recent camouflet that had forestalled and eliminated German countermining in the vicinity. Despite the shattered ground and the mangled timbering the collapsed section was quickly recovered.
Some 5km along the frontline to the right the Hollandscheschuur Farm Tunnel had been driven 240m across no-man'sland by early June despite persistent flooding and counter mining as well as accurate mortar fire from the Germans. At Peckham to the south ground pressures were very high; support which had been adequate in other tunnels snapped and had to be replaced with 175mm balks of wood.
But at Petit Bois the supposed Achilles Heel of the plan where both a new tunnelling technique and a tunnelling machine had failed men of 250 TC had kicked their way for 485m to the point where the tunnel branched to allow two mines to be placed. Some 13 tunnellers were down at that junction early on the morning of 10 June 1916 when the Germans detonated two charges, collapsing a length of tunnel and entombing the men. The rescuers found the tunnel blocked at about 380m and although chances of survival were considered poor Cropper ordered an all-out rescue attempt. Rather than try to clear the 100m or so of mangled debris it was decided to drive a bypass tunnel alongside; spurred by the plight of their trapped comrades the rescuers tunnelled with incredible energy averaging over 12m advances per day compared with 4.5m normally. Finally they broke through after six and a half days to find that only the doughty sapper William Bedson was still alive; all his companions had indeed survived the blast but had died before help could reach them. Work on the tunnel was immediately restarted and advanced to 548m where it once again branched right and left into shortish galleries, some 79m and 64m long respectively, and two heavy charges were subsequently placed.
But by now mid-June 1916 was upon them. Most progress had been made along the southernmost 5.5km where 171 TC had laid five mines. One of 30,000lb (13,608kg) of ammonial was in a tunnel that had started in Ploegsteert Wood and had been charged and wired in February. Similarly two mines had been placed in a tunnel from Trench 127; one of 36,000 (16,330kg) ammonal on 20 April and the second larger charge of 50,000 (22,680kg) ammonal less than three weeks later. Then in mid-May and June two further charges had been placed in the forked tunnel starting from Tench 122. Some of the great and good seemed to be in on this act as Winston Churchill was in charge of a batallion of the 6th Royal Scots Fusiliers stationed in Ploegsteert Wood during the opening four months of 1916 following his resignation the previous November as First Lord of the Admiralty after the Gallipoli debacle.
Finally 171 TC was preparing the sixth mine at Spanbroeknolen with massive charge of 91,000 (41,278kg) ammonal packed in 1,820 sealed tins each weighing 50lbs (23kg). The charging, wiring and tamping were all completed by 25 June 1916 but still there was no news on the Flanders attack date. With French forces being inexorably sucked into the bloodbath at Verdun the campaign at the Somme became a mainly British undertaking. An attack at Messines would have to wait.
With both sides so heavily engaged to the south there was time to complete the tunnels already underway at the end of June 1916. Five were ready charged, wired and tamped – one each at Hollandscheschuur, Petit Bois and Peckham with a pair at Kruisstraat. A further four were added in August at Hill 60, Hollandschuur, Petit Bois and Kruisstraat. Finally a mine was placed at Caterpillar in October 1916 and at Kruisstraat in April 1917 to complete these tunnels. New tunnels were started at St Eloi in August 1916 and at Maedelstede Farm in September to complete the mines that would be blown in the attack on Messines Ridge.
There were two major problems which made this approach problematic. The mines would be in the ground for many months – over a year as it turned out in some instances – exposed to the risk of discovery and countermining by the Germans and to deterioration of the explosives and wiring due to moisture. Ammonal, the main explosive used, was highly absorbent and unreliable when its moisture content exceeded four per cent, so the effectiveness of the sealed tins in which it was supplied was crucial.
The suspense was soon increased at Petit Douve Farm on 24 August 1916 when a spur tunnel off a deep gallery beneath the farm drove unexpectedly into a German tunnel. As the collision could not be concealed an exchange of camouflets ensued which resulted in the abandonment of the gallery and the charge already placed in it.
In mid-February 1917 the last of the succession of German camouflets at Spanbroekmolen did extensive damage; the wiring had completely failed and 120m of tunnel was beyond repair. Work was begun by 171 TC to drive a bypass alongside and although there were grave misgivings whether the new tunnel would be completed in time it made it with less than a day to spare. Indeed the end was nigh. At the meeting between the British Commander-in-Chief Douglas Haig and General Herbert Plumer commander in the forces in the Ypres Salient on 7 May it was agreed that an attack on Messines Ridge would take place in a month's time on 7 June 1917. The opening gambit at zero hour was to be the firing of 19 mines along the 16km front. But there were still some doubts even at this late stage; three mines were still being excavated or charged and the one at Spanbroekmolen had to be repaired.
The northern most mines consisted of 53,500lb (24,268kg) mixture of ammonal and gun cotton and 70,000lb (31,8075kg) ammonal under Hill 60 and Caterpillar spoil heaps respectively. Both had been laid from the Berlin Tunnel from autumn of 1916 by the third Canadian TC, which had been relieved by the first Australian TC in November. The latter had sunk a steel shaft to replace the seriously leaking and fragile incline there and were being constantly harassed by the enemy both below and above ground. With only three days to go the Germans were detected advancing towards the charges but at a rate, even if their tunnel drive was accurate, too slow to find them before zero hour.
At St Eloi just over 3km to the southwest was the largest charge of the war, a massive 95,600lbs (43,364kg) of ammonal laid at a depth of 38m by 1st Canadian TC. Work on the 503m tunnel had started mid-August 1916 and charging was completed on 28 May 1917 with just nine days to spare.
Southwards from St Eloi came the seven mines laid by 250 TC. First a cluster of three mines laid in branches from a single tunnel at Hollandscheschuur completed in June, July and August 1916. Then 900m or so to their right were twin mines each of 30,000lbs (13,608kg) of ammonal and blastine, one at the end of the 631m tunnel, the other in a 64m branch from it at Petit Bois – the scene of the Sapper Benson ordeal and the abortive efforts to tunnel through the clay by the Stanley Heading machine. Next came Maedelstede Farm where 94,000lbs (42,638kg) mostly ammonal was completed on 2 June a mere four days before zero hour. And lastly at Peckham Farm where the drive had been plagued with inflows of water, mud and saturated sand and swelling ground; then in January 1917 a section of tunnel collapsed and a 20,000lbs (4,072kg) mine was irretrievably lost; a bypass tunnel was driven and the wiring to the 87,000lbs (39,463kg) charge reinstated.
Nearby, at Spanbroekmolen the situation was fraught to the bitter end. As already described a 91,000lbs (41,278kg) ammonal charge had been laid in June 1916 by 171 TC and all remained quiet until February 1917. Then the driving of a branch tunnel to place a second mine alerted the Germans to the situation and their retaliatory series of camouflets ruptured the leads to the mine already in place. Again a bypass tunnel had to be driven to recover the situation a priming charge of dynamite being placed hard against the ammonal with just hours to spare.
Proceeding southwards the threesome of mines at Kruisstraat came next and the longest, 658m, tunnel of them all. Again the work of 171 TC, these mines one of 49,500lb (22,453kg) and two each of 30,000 (13,608kg) mainly of ammonal were located to neutralise the German front, support and reserve trench lines. The 60,000lb (27,216kg) ammonal mine at Ontario Farm followed. Here again there was a desperate race against time but once more 171 Tunnelling Company won and accomplished their task with only a few hours in hand.
The last four mines to the south of Ontario farm had all been placed between late April and mid June 1916 and had laid there undisturbed for over a year. However on 4 June 1917 a stray shell damaged a 21m deep shaft carrying the leads from the pair of mines at Trench 122, necessitating rewiring; the repairs were completed by Lieutenant Cecil Hall of 3rd Canadian TC with just 20 minutes to spare. All was now ready for the big blow, the culmination of Norton-Griffiths' Big Idea. More than 100,000 troops were massed for the assault at zero hour, 03.10 hours, on 17 June 1917. At about 03.30 hours the mine at Peckham Farm was detonated; Spanbroekmolen was fired 20 seconds later with, Kruisstraat two seconds behind and so on. All 19 mines charged with a total of 933,200lb (423,300kg) explosives had been blown virtually simultaneously, a magnificent achievement for the tunnellers.
The Battle of Messines was now on. By 07.00hrs the villages of Messines and Wytschaete were captured and by midday the fighting had moved well beyond the ridge crest towards the final objectives. The demoralising effects of the mines on the defenders had been overwhelming. German soldiers were seen staggering about, weeping, scrabbling on hands and knees and utterly confused. The attackers had expected stiff resistance but much of the advance was virtually unopposed. Total German casualties are not known, but 10 officers and 679 men died at Hill 60 and Caterpillar alone; a further 400 were obliterated by the St Eloi blast. Extrapolations from these examples are problematic since these sectors were heavily manned. Elsewhere trenches were often lightly manned. Further to the south, opposite Trench 121 and just outside the scope of the assault the local German commander had ordered a limited withdrawal, which would have completely negated the effects of mining.
CONCLUSION
The capture of Messines Ridge was a key episode in the First World War; the swift victory was a spectacular triumph stemming from the nerve-racking, painstaking and courageous efforts of the tunnellers over the one and a half years. But it was also the end of large scale mining warfare by the armies of the major powers. However, tunnels can still play a crucial role when the geology is favourable as the Viet Cong showed with their Cu Chi tunnel system in the Vietnam conflict.
