The Actions of St Eloi Craters from 27 March to 16 April 1916, were local operations in the Ypres Salient of Flanders, during the First World War by the German 4th Army and the British Second Army. Sint-Elooi (the French St Eloi is commonly used in English) is a village about 5 km (3.1 mi) south of Ypres in Belgium. The British dug six galleries under no man's land, placed large explosive charges under the German defences and blew them at 4:15 a.m. on 27 March. The 27th Division captured all but craters 4 and 5. The 46th Reserve Division counter-attacked but the British captured craters 4 and 5 on 30 March. The Canadian Corps took over, despite the disadvantage of relieving troops in action.
The Canadians inherited positions in a deplorable state, the British having pressed their advantage, rather than consolidating the captured ground. On the night of 5/6 April,, a German methodical attack (Gegenangriff) recovered the craters. Canadian runners struggled to deliver messages and for several days, the Canadian and British staffs were ignorant of which craters had been captured, the topography having been changed so much by the mine detonations. There were 17 craters, the new ones superimposed on the old, the ground full of shell-holes and derelict trenches. Snipers made it impossible to orientate and fresh troops easily mistook one pair of craters for another.
The Canadians counter-attacked several times, then concentrated on consolidating the front line, ready for another attempt. Constant rain, oozing mud and incessant artillery-fire exhausted troops quickly and battalions had to be relieved after a couple of days. Canadian and British staffs were still ignorant of the German capture of craters 4 and 5. Conflicting reports added to the uncertainty but a reconnaissance by a Canadian major on 10 April found that the Germans were in crater 4. On 16 April, the Royal Flying Corps (RFC) photographed the area, showing the Germans in craters 2, 3, 4 and 5 and a trench round the front lips. Plans to attack were cancelled and for two weeks both sides exchanged artillery-fire.
The mud and poor weather caused unprecedented misery on the troops but the first attack showed that with preparation, surprise and good timing, a limited objective attack could succeed. The British had attacked with tired troops, had not achieved all of their objectives and the second attempt was at the cost of quick consolidation. At St Eloi, against an attack on a narrow front, where the defender had good observation, the ground could not be held. It was an open question as to what width of front to attack, narrow enough to guarantee success, yet wide enough to force the Germans to disperse their artillery-fire so that captured ground could be held.
Background
Ypres district
Ypres lies at the junction of the Ypres–Comines Canal and the Ieperlee. The city is overlooked by Kemmel Hill in the south-west and from the east by low hills running south-west to north-east, with Wytschaete (Wijtschate), Hill 60 to the east of Verbrandenmolen, Hooge, Polygon Wood and Passchendaele (Passendale). The high point of the ridge is at Wytschaete, 7,000 yd (4.0 mi; 6.4 km) from Ypres, while at Hollebeke the ridge is 4,000 yd (2.3 mi; 3.7 km) distant and recedes to 7,000 yd (4.0 mi; 6.4 km) at Polygon Wood. Wytschaete is about 150 ft (46 m) above the plain; on the Ypres–Menin road at Hooge, the elevation is about 100 ft (30 m) and 70 ft (21 m) at Passchendaele. The rises are slight, apart from the vicinity of Zonnebeke, which has a gradient of 1:33.
From Hooge and to the east, the slope is 1:60 and near Hollebeke, it is 1:75; the heights are subtle but have the character of a saucer lip around Ypres. The main ridge has spurs sloping east and one is particularly noticeable at Wytschaete, which runs 2 mi (3.2 km) south-east to Messines (Mesen), with a gentle slope to the east and a 1:10 decline to the west. Further south is the muddy valley of the Douve river, Ploegsteert Wood (Plugstreet to the British) and Hill 63. West of Messines Ridge is the parallel Wulverghem (Spanbroekmolen) Spur; the Oosttaverne Spur, also parallel, is to the east. The general aspect south of Ypres is of low ridges and dips, gradually flattening to the north into a featureless plain.
In 1914, Ypres had 2,354 houses and 16,700 inhabitants inside medieval earth ramparts faced with brick and a ditch on the east and south sides. Possession of the higher ground to the south and east of the city, gives ample scope for ground observation, enfilade fire and converging artillery-fire. An occupier also has the advantage of artillery deployments and the movement of reinforcements and supplies being screened from view. The ridge had woods from Wytschaete to Zonnebeke, giving good cover, some being of notable size, like Polygon Wood and those later named Battle Wood, Shrewsbury Forest and Sanctuary Wood.
The woods usually had undergrowth but the fields in gaps between the woods were 800–1,000 yd (730–910 m) wide and devoid of cover. Roads in this area were usually unpaved, except for the main ones from Ypres, with occasional villages and houses. The lowland west of the ridge was a mixture of meadow and fields, with high hedgerows dotted with trees, cut by streams and ditches emptying into the canals. The Ypres–Comines Canal is about 18 ft (5.5 m) wide and the Yperlee about 36 ft (11 m); the main road to Ypres from Poperinge to Vlamertinge is in a defile, easily observed from the ridge.
1915
January 1915 was a month of rain, snow and floods, made worse for both sides by artillery-fire, sniping and the need for constant trench repairs. The British front was extended when the 27th Division and the 28th Division arrived in France and took over from the French XVI Corps. The British divisions had only seventy-two 18-pounders between them and had to hold the front line with far more men to compensate, the French being able to defend an outpost line with a hundred and twenty 75 mm, twenty-four 90 mm and six 120 mm guns. On 21 February, the Germans blew a mine in Shrewsbury Forest, north of Klein Zillebeke, captured an area of 100 yd × 40 yd (91 m × 37 m) and inflicted 57 casualties. Constant underground fighting began in the Ypres Salient at Hooge, Hill 60, Railway Wood, Sanctuary Wood, St Eloi and The Bluff. The British formed specialist tunnelling companies from soldiers who had been miners and tunnellers in civilian life, that began to reach France at the end of February. German troops attacked the 28th Division near St Eloi on 4 February and held the captured ground for several days. Further south, the 27th Division was attacked on 14 and 15 February; on 28 February, the 27th Division made a successful local attack along with Canadian troops.
British tunnelling companies
There was no British army mining organisation in 1914, except for a short course for Royal Engineers but after the First Battle of Ypres in 1914, siege warfare and mining began and the British realised that the Field and Siege Companies RE were in too great a demand to provide men for mining. On 3 December, Lieutenant-General Henry Rawlinson asked for a specialist battalion of sappers and miners and on 28 December the War Office was requested to send 500 clay kickers, civilian specialists in tunnelling through clay. The British Expeditionary Force (BEF) was ordered to form Brigade Mining Sections with miners and tunnellers already in the army. In February 1915, it was decided to form eight tunnelling companies from civilians recruited in Britain and transfers from the army. Another twelve companies were formed later in 1915, one in 1916, a Canadian Tunnelling Company was formed in December 1915, two more arrived in France in March 1916 and a New Zealand and three Australian tunnelling companies arrived in May. Counter-mining by the Tunnelling Companies RE began at St Eloi in the spring of 1915. Much of the mining in this sector was done by the 177th Tunnelling Company and the 172nd Tunnelling Company.
The Ypres area has a shallow soil layer of loam or sand above waterlogged semi-liquid sand and slurry patches of sand and clay. Beneath the second layer is a thick seam of blue clay. The early mining took place above the blue clay which put very heavy pressures of water and wet sand on the underground works. In August the digging of galleries had begun, to be completed by the end of June 1916. Both sides spent 1915 mining and counter-mining, the British springing 13 mines and 29 camouflets against 20 German mines and 2 camouflets. In September, Brigadier-General George Fowke the Engineer in Chief, proposed a mining offensive in the blue clay 60–90 ft (18–27 m) underground. Since the Germans were on the higher ground, galleries could be driven horizontally into the blue clay from shafts about 300–400 ft (91–122 m) back from the front line. By January 1916, the 172nd Tunnelling Company had sunk shafts into the blue clay and began to dig galleries 80–120 ft (24–37 m) under the German front position. After the Second Army offensive in the summer of 1916 was postponed, the mining offensive was made even more ambitious with a plan to mine Messines Ridge.
Action of St Eloi
On 14 March 1915, the Germans attacked St Eloi after springing two mines and captured the village, trenches nearby and the Mound, a spoil heap about 30 ft (9.1 m) high and 0.5 acres (0.20 ha) in area, on the west side of a rise, south of the village. The 80th Brigade of the 27th Division had fought hand-to-hand with the attackers but could not counter-attack because of a lack of close reserves and German artillery barrages isolating the attack front. Just after midnight, two battalions managed to attack and retook the village and the lost trenches. The Mound was not regained as the Germans had managed to consolidate and retained the advantage of observation from it. Another German attack on 17 March was a costly failure and on 14 April, after a four-day bombardment, the Germans blew another mine at 11:15 p.m. and commenced a systematic bombardment, against which the British artillery replied but no infantry attack followed.
Prelude
British preparations
After the German attack at the Bluff, the V Corps commander, Lieutenant-General Herbert Plumer, decided that it would be more advantageous to make a retaliatory attack at St Eloi, about 1 mi (1.6 km) to the west. Since an attack on 14 March 1915, the Germans had held a salient 600 yd (550 m) wide and 100 yd (91 m) deep around the Mound, against which an attack had been planned in November 1915. The salient was on a slight spur that ran down from the higher ground around Ypres, which gave a commanding view over the British lines. An attack on the Mound required mines to be sunk much deeper and work by the 172nd Tunnelling Company had begun in August 1915. Three shafts were dug 50–60 ft (15–18 m) deep and by November, when the Germans blew a mine at the Bluff, a line of shallow galleries had been dug. Work on the deep mines continued for a possible operation in February 1916; eventually it was decided to dig six galleries from the deep shafts. After another German mine explosion at the Bluff in January, work on the shallow mines was stopped and all efforts were made to finish the deep galleries at St Eloi.
German miners could be heard above the deep galleries, that showed that the galleries had been advanced under the German lines but the British deep mines, D1, D2, H1, H4 and F appeared to be safe from discovery. Work was stopped on mine I, the furthest west, that was thought to be most vulnerable to exposure. On 10 March 1916, the Germans blew a camouflet which collapsed 20 ft (6.1 m) of the gallery. The British blew their own camouflet on 24 March, which collapsed more of the gallery and a charge was placed 240 ft (73 m) along, even though the German trenches were 420 ft (130 m) away. F gallery was dug at 38 ft (12 m) and then stopped when it ran into German defensive mines about 100 ft (30 m) from the German lines.
Work continued in the higher galleries and the British tunnellers entered two German galleries and demolished them. There were four central galleries, two laid from shaft D and two from shaft H. (For most of the time, the British preparations were obstructed by an efficient German counter-mining effort but the British carried away excavated earth in sacks by hand, dumped it in dips unseen and then camouflaged the dumps.) From Kemmel Hill, a hollow south of St Eloi could be observed and was thought to be a German assembly area. No artillery fire was directed on the area, but a code word was arranged at which the guns were to open rapid fire.
German preparations
The 46th Reserve Division (Generalleutnant von Wasielewski), part of the XXIII Reserve Corps (General Hugo von Kathen) which had been in the Ypres area since late 1914, took over from the 123rd Division on 23 March, with both brigades in the line, the 92nd Brigade and the attached Reserve Jäger Battalion 18 (RJB 18) taking over at St Eloi. The German mines in the area had become waterlogged and dilapidated but the 123rd Division engineers had been confident that a British mine attack was unlikely and air reconnaissance had revealed no obvious preparations for an attack. More artillery positions had been detected near Kruisstraat and Dickebusch Lake and huts had been built near Wulverghem and Vierstraat but this had not been seen as suspicious. During the night of 25/26 March, the III Battalion, Reserve Infantry Regiment 216 (RIR 216) was relieved by RJB 18, with I Battalion, RIR 216 in close reserve. On the afternoon of 26 March a listening post overheard British troops discussing mines to be fired at St Eloi but a careful inspection by German tunnellers found no cause for alarm. As a precaution, RJB 18 thinned its front line to keep more troops in the support trenches and it was a quiet night.