page_title: Mines on the first day of the Somme
section_title: III Corps
hierarchical_section_title: Mines on the first day of the Somme / Prelude / III Corps
caption_attribution_description: Map showing location of "Sausage Valley" south of La Boiselle, as at 1 July 1916 during the Battle of Albert.
context_page_description: The 19 mines on the first day of the Somme comprised a series of underground explosive charges, secretly planted by British tunnelling units beneath the German front lines on the Western Front during the First World War, ready to be detonated in the morning of Saturday 1 July 1916, the first day of the Battle of the Somme. The joint explosion of these mines ranks among the largest artificial non-nuclear explosions.
  The tunnelling companies of the Royal Engineers were to make two major contributions to the opening attack of the Battle of the Somme: Firstly, by preparing a number of large and small mines; and secondly, by preparing a series of shallow Russian saps from the British front line into no man's land, which would be opened at Zero Hour and allow the infantry to attack the German positions from a comparatively short distance.
  The 19 mines consisted of eight large and eleven small charges deep in the chalky ground which were "overcharged" to throw up high lips for screening and to give advantage to the attackers when they captured the resulting craters.
context_section_description: In the British front sector allocated to III Corps at La Boisselle, four mines were prepared: Two charges (known as No 2 straight and No 5 right) were planted at L'îlot at the end of galleries dug from Inch Street Trench by the 179th Tunnelling Company, intended to wreck German tunnels and create crater lips to block enfilade fire along no man's land. As the Germans in La Boisselle had fortified the cellars of ruined houses, and cratered ground made a direct infantry assault on the village impossible, two further mines, known as Y Sap  and Lochnagar after the trenches from which they were dug, were laid on the north-east and the south-east of La Boisselle to assist the attack on either side of the German salient in the village – see map.
  The 185th Tunnelling Company started work on the Lochnagar mine on 11 November 1915 and handed the tunnels over to 179th Tunnelling Company in March 1916. A month before the handover, 18 men of the 185th Tunnelling Company (2 officers, 16 sappers) were killed on 4 February when the Germans detonated a camouflet near the British three-level mine system, starting from Inch Street, La Boisselle, the deepest level being just above the water table at around 30 metres (100 ft). The Lochnagar mine consisted of two chambers with a shared access tunnel (see map). The shaft was sunk in the communication trench called Lochnagar Street. After the Black Watch had arrived at La Boissselle at the end of July 1915, many existing Allied fortifications, originally dug by the French, had been given Scotland-related names. The Lochnagar mine probably had the first deep incline shaft, which sloped 1:2–1:3 to a depth of about 29 metres (95 ft) – see map. It was begun 91 metres (300 ft) behind the British front line and 270 metres (900 ft) away from the German front line. Starting from the inclined shaft, about 15 metres (50 ft) below ground, a gallery was driven towards the German lines. For silence, the tunnellers used bayonets with spliced handles and worked barefoot on a floor covered with sandbags. Flints were carefully prised out of the chalk and laid on the floor; if the bayonet was manipulated two-handed, an assistant caught the dislodged material. Spoil was placed in sandbags and passed hand-by-hand, along a row of miners sitting on the floor and stored along the side of the tunnel, later to be used to tamp the charge. When about 41 metres (135 ft) from the Schwabenhöhe, the tunnel was forked into two branches and the end of each branch was enlarged to form a chamber for the explosives, the chambers being about 18 metres (60 ft) apart and 16 metres (52 ft) deep – see map. When finished, the access tunnel for the Lochnagar mine was 1.37 by 0.76 metres (4.5 ft × 2.5 ft) and had been excavated at a rate of about 46 centimetres (18 in) per day, until about 310 metres (1,030 ft) long, with the galleries beneath the Schwabenhöhe. The mine was loaded with 27,000 kilograms (60,000 lb) of ammonal, divided in two charges of 16,000 kilograms (36,000 lb) and 11,000 kilograms (24,000 lb). As the chambers were not big enough to hold all the explosive, the tunnels that branched to form the 'Y' were also filled with ammonal. The longer branch was 18 metres (60 ft) long, the shorter was 12 metres (40 ft) long. The tunnels did not quite reach the German front line but the blast would dislodge enough material to form a 4.6 metres (15 ft) high rim and bury nearby trenches.
  The tunnel for the Y Sap mine underneath the German trenches overlooking Mash Valley just north of La Boisselle started in the British front line near where it crossed the D 929 Albert–Bapaume road, but because of German underground defences it could not be dug in a straight line. About 460 metres (500 yd) were dug into no man's land, before it turned right for about another 460 metres (500 yd). About 18,000 kilograms (40,000 lb) of ammonal was placed in the chamber beneath the Y Sap mine. The Lochnagar and the Y Sap mines were "overcharged" to ensure that large rims were formed from the disturbed ground. Communication tunnels were also dug for use imm
caption: Map of La Boisselle with British movements on 1 July 1916
exif: {}