Y Sap mine

Y Sap mine
Part of the Battle of the Somme, First World War
Battle of the Somme 1 July – 18 November 1916
Date 1 July 1916 Location Picardy, France 50°01′14.5″N 02°41′24.1″E / 50.020694°N 2.690028°E / 50.020694; 2.690028Coordinates: 50°01′14.5″N 02°41′24.1″E / 50.020694°N 2.690028°E / 50.020694; 2.690028 Result German victory
Belligerents
British Empire	Germany
Commanders and leaders
Douglas Haig	General Erich von Falkenhayn
Y Sap mine (La Boisselle) Site of the Y Sap mine, near La Boisselle

The Y Sap mine was an underground explosive charge, secretly planted by the British during the First World War and ready for 1 July 1916, the first day on the Somme. The mine was dug by the Tunnelling Companies of the Royal Engineers under a German machine-gun nest known as Blinddarm (appendix) in the front line, on the north side of the village of La Boisselle in the Somme département. The mine was named after Y Sap, the British trench from which the gallery was driven. It was one of 19 mines that were placed beneath the German lines on the British section of the Somme front to assist the infantry advance at the start of the battle. The Y Sap mine was sprung at 7:28 a.m. on 1 July 1916 and left a large crater. The explosion of the Y Sap mine failed to assist the British attack as the German eavesdroppers at the "Moritz 28 North" listening station intercepted and passed on the British "good luck" message. The Germans moved their machine-guns from the Blinddarm and at Zero Hour the machine-gunners caught the British infantry in crossfire. The 34th Division had the highest number of casualties of any of the divisions involved on 1 July. The crater of the Y Sap mine was filled in after World War I and is no longer visible.

French and German military operations began on the Somme in September 1914. A German advance westwards towards Albert was stopped by the French at La Boisselle and attempts to resume mobile warfare in October failed. Both sides reduced their attacks to local operations or raids and began to fortify their remaining positions with underground works. On 18 December, the French captured the La Boisselle village cemetery at the west end of a German salient and established an advanced post only 3 m (3.3 yd) from the German front line. By 24 December, the French had forced the Germans back from the cemetery and the western area of La Boisselle but were stopped a short distance forward at L'îlot de La Boisselle, in front of German trenches protected by barbed wire. Once the location of a farm and a small number of buildings, L'îlot became known as Granathof (Shell Farm) to the Germans, and later as the Glory Hole to the British. On Christmas Day 1914, French engineers sank the first mine shaft at La Boisselle.