Mines in the Battle of Messines (1917)

British mining, 1915–1916

As part of allied operations in the Ypres Salient, British mining against the German-held salient at Wijtschate near Messines had begun in spring 1915, with diggings 4.6–6.1 metres (15–20 ft) below the surface. The concept of a deep mining offensive was devised in September 1915 by the Engineer-in-Chief of the BEF, Brigadier George Fowke, who proposed to drive galleries 18–27 metres (60–90 ft) underground. Fowke had been inspired by the thinking of Major John Norton-Griffiths, a civil engineer, who had helped form the first tunnelling companies and introduced the quiet clay kicking technique.

In September 1915, Fowke proposed to dig under the Ploegsteert–Messines (Mesen), Kemmel–Wytschaete (Wijtschate) and Vierstraat–Wytschaete roads and to dig two tunnels between the Douve river and the south-east end of Plugstreet (Ploegsteert) Wood, the objectives to be reached in three to six months. Fowke had wanted galleries about 960 metres (1,050 yd) long, as far as Grand Bois and Bon Fermier Cabaret on the fringe of Messines but the longest tunnel was a 660 metres (720 yd) gallery to Kruisstraat. The scheme devised by Fowke was formally approved on 6 January 1916, although Fowke and his deputy, Colonel R. N. Harvey, had already begun the preliminaries. By January 1916, several deep mine shafts, marked as "deep wells" and six tunnels had thus been started. Sub-surface conditions were especially complex and separate ground water tables made mining difficult. To overcome the technical difficulties, two military geologists assisted the miners from March 1916, including Edgeworth David, who planned the system of mines.

Co-ordinated by the Royal Engineers, the mine galleries were dug by the British 171st, 175th and 250th Tunnelling companies and the 1st Canadian, 3rd Canadian and 1st Australian Tunnelling companies, while the British 183rd, 2nd Canadian and 2nd Australian Tunnelling companies built dugouts (underground shelters) in the Second Army area. Sappers dug the tunnels into a layer of "blue clay" 24–37 metres (80–120 ft) below the surface, then drifted galleries (horizontal passages) for 5,453 metres (5,964 yd) to points beneath the position of the German Group Wytschaete, despite German counter-mining. German tunnellers came within metres of several British mine chambers and, well before the Battle of Messines, found La Petite Douve Farm mine. On 27 August 1916, the Germans set a camouflet, which killed four men and wrecked the chamber for 120 metres (400 ft); the mine had been charged and the explosives were left in the gallery. A gallery of the Kruisstraat mine, begun on 2 January 1916, had been dug for 690 metres (750 yd) and was flooded by a camouflet explosion in February 1917, after which a new chamber was dug and charged next to the flooded mine. The British diverted the attention of German miners from their deepest galleries by making many minor attacks in the upper levels.

British mining, 1917

The BEF miners eventually completed a line of deep mines under Messines Ridge that were charged with 454 tonnes (447 long tons) of ammonal and gun cotton. Two mines were laid at Hill 60 on the northern flank, one at St Eloi, three at Hollandscheschur Farm, two at Petit Bois, single mines at Maedelstede Farm, Peckham House and Spanbroekmolen, four at Kruisstraat, one at Ontario Farm and two each at Trenches 127 and 122 on the southern flank. A group of four mines was placed under the German strongpoint Birdcage at Le Pelerin, just outside Ploegsteert Wood. The large mines were at St Eloi, charged with 43,400 kilograms (95,600 lb) of ammonal, at Maedelstede Farm, which was charged with 43,000 kilograms (94,000 lb), and Spanbroekmolen on one of the highest points of the Messines Ridge, which was filled with 41,000 kilograms (91,000 lb) of ammonal. The mine at Spanbroekmolen was set 27 metres (88 ft) below ground, at the end of a gallery 520 metres (1,710 ft) long.

When detonated on 7 June 1917, the blast of the mine at Spanbroekmolen formed the "Lone Tree Crater" with a diameter of 76 metres (250 ft) and a depth of 12 metres (40 ft).) The mine at Ontario Farm did not produce a crater but left a shallow indentation in the soft clay, after wet sand flowed back into the crater. Birdcage 1–4 on the extreme southern flank in the II Anzac Corps area, were not required because the Germans made a local retirement before 7 June. Peckham 2 was abandoned due to a tunnel collapse and the mine at La Petite Douve Farm was abandoned after the German camouflet blast of 27/28 August 1916. The evening before the attack, Harington, the Second Army Chief of Staff, remarked to the press, "Gentlemen, we may not make history tomorrow, but we shall certainly change the geography".

German mining, 1916–17

In December 1916, Oberstleutnant Füßlein, commander of German mining operations in the salient, had recorded that British deep mining was intended to support an offensive above ground and received three more mining companies, to fight in the British lower as well as the upper mine systems and had gained some success. In April 1917, the 4th Army (General Friedrich Bertram Sixt von Armin) received information from air reconnaissance that a British offensive was being prepared in the Messines Ridge sector and a spy reported to OHL, that if the offensive at Arras was frustrated, the British would transfer their effort to Flanders. Hermann von Kuhl, the Chief of Staff of Heeresgruppe Kronprinz Rupprecht (Army Group Crown Prince Rupprecht), suggested that the salient around Messines Ridge be abandoned, since it could be attacked from three sides and most of the defences were on forward slopes, vulnerable to concentric, observed artillery-fire. A voluntary retirement would avoid the calamity experienced by the defenders at the Battle of Vimy Ridge on 9 April.

Kuhl proposed a retirement to the Sehnen Line (Oosttaverne Line to the British), halfway back from the Second Line along the ridge or all the way back to the Third Line (Warneton Line). At a conference with 4th Army commanders to discuss the defence of Messines Ridge on 30 April, most of them rejected the suggestion, because they considered that the defences had been modernised, were favourable for a mobile defence and convenient for counter-attacks. The artillery commander of Gruppe Wijtschate said that the German guns were well-organised and could overcome British artillery. The divisional commanders were encouraged by a report by Füßlein on 28 April, that the counter-mining had been such a success, particularly recently that

A subterranean attack by mine-explosions on a large scale beneath the front line to precede an infantry assault against the Messines Ridge was no longer possible. (nicht mehr möglich)

For this and other reasons the withdrawal proposal was dropped as impractical (nicht tünlich). Soon after the conference, Füßlein changed his mind and on 10 May, reported to the 4th Army his suspicions that the British might have prepared several deep mines, including ones at Hill 60, Caterpillar, St. Eloi, Spanbroekmolen and Kruisstraat and predicted that if an above-ground offensive began, there would be big mine explosions in the vicinity of the German front line.

On 19 May, the 4th Army concluded that the greater volume of British artillery fire was retaliation for the increase in German bombardments and although defensive preparations were to continue, no attack was considered imminent. On 24 May, Füßlein was more optimistic about German defensive measures and Laffert wrote later, that the possibility of mine explosions was thought remote and if encountered they would have only local effect, as the front trench system was lightly held. From 12 May, weekly reports by the 4th Army made no mention of mining and Rupprecht made no reference to it after the end of the month. Other officers like Oberstleutnant Wetzell and Oberst Fritz von Lossberg, wrote to OHL warning of the mine danger and the importance of forestalling it by a retirement and were told that it was a matter for the commanders on the spot.

Battle: 7 June 1917

The artillery fire was lifted half an hour before dawn, and as they waited in the silence for the offensive to begin, some of the troops reportedly heard a nightingale singing. Starting from 3.10 a.m. on 7 June 1917, the mines at Messines were fired within the space of 20 seconds. The joint explosion ranks among the largest non-nuclear explosions of all time and surpassed the mines on the first day of the Somme fired 11 months before. The sound of the blast was considered the loudest man-made noise in history. Reports suggested that the sound was heard in London and Dublin, and at Lille University's geology department, the shock wave was mistaken for an earthquake. Some eyewitnesses described the scene as "pillars of fire", although many also conceded that the scene was indescribable.

Suddenly at dawn, as a signal for all of our guns to open fire, there rose out of the dark ridge of Messines and "Whitesheet" and that ill-famed Hill 60, enormous volumes of scarlet flame [...] throwing up high towers of earth and smoke all lighted by the flame, spilling over into fountains of fierce colour, so that many of our soldiers waiting for the assault were thrown to the ground. The German troops were stunned, dazed and horror-stricken if they were not killed outright. Many of them lay dead in the great craters opened by the mines.

The fact that the detonations were not simultaneous enhanced their effect on the German troops. Strange acoustic effects also added to the panic – German troops on Hill 60 thought that the Kruisstraat and Spanbroekmolen mines were under Messines village, which was located well behind their front line, while some British troops thought that they were German counter-mines going off under the British support trenches. The combined explosion is considered to have killed more people than any other non-nuclear man-made explosion in history; it killed approximately 10,000 German soldiers between Ypres and Ploegsteert.

Analysis

Two days after the battle, General Maximilian von Laffert the Gruppe Wijtschate commander was sacked and the German official history, Der Weltkrieg (volume XII, 1939), placed the mines, which were unprecedented in size and number, second in a list of five reasons for the German defeat. In an after-action report, Laffert wrote that had the extent of the mine danger been suspected, a withdrawal from the front trench system to the Sonne Line, halfway between the First and Second lines, would have been ordered before the attack, since the cost inflicted on the British by having to fight for the ridge justified its retention. In 1929, Hermann von Kuhl lamented the failure to overrule the 4th Army commanders on 30 April and prevent "one of the worst tragedies of the war".

The Battle of Messines was regarded as the most successful local operation of the war but it left a legacy: six mines were not used. Four on the extreme southern flank were not required because the ridge fell so quickly, and another, a 20,000-pound (9,100 kg) mine codenamed Peckham, was abandoned before the attack due to a tunnel collapse. The sixth, and one of the biggest, was planted under a ruined farm called La Petite Douve. It was lost when the Germans mounted a counter-mining attack, and never used. After the war, La Petite Douve was rebuilt by its owners, the Mahieu family, and later renamed La Basse Cour. The mine is beneath a barn, next to the farmhouse.