http://en.wikipedia.org/wiki/Battle_of_Messines
Battle of Messines
The Battle of Messines was a battle of the western front of World War I. It began on 7 June 1917 when the British Second Army under the command of General Herbert Plumer launched an offensive near the village of Mesen (Messines) in West Flanders, Belgium. The target of the offensive was a ridge running north from Messines village past Wytschaete village which created a natural stronghold southeast of Ypres. One of the key features of the battle was the detonation of 19 mines immediately prior to the infantry assault, a tactic which disrupted German defences and allowed the advancing troops to secure their objectives in rapid fashion.
The assault on Messines ridge was conceived in early 1916, as Plumer sought ways to break German control of important strategic locations in the Ypres area. When it became apparent that the French offensive on the River Aisne would not succeed, General Douglas Haig reconceived the Messines operation as a precursor to a larger assault in the Ypres sector and ordered Plumer to proceed with the attack as soon as possible. Not only would capturing Messines Ridge give the British control of important strategic ground, it would also flatten out the southern flank of the Ypres Salient. This would both reduce the manpower needed to maintain the front, and reduce the German strategic and tactical advantages in the area.
Mining operations
Over a period beginning more than a year before the attack, Canadian, Australian, and British engineers tunnelled under the German trenches and laid 21 mines totaling 455 tonnes of ammonal explosive. To solve the problem of wet soil, the tunnels were made in the layer of "blue clay", 80–120 feet (25–30 m) below the surface. The galleries dug in order to lay these mines totalled over 8,000 yards (7,300 m) in length, and had been constructed in the face of tenacious German counter-mining efforts. On several occasions, German tunnellers were within metres of large British mine "chambers". One mine was found by the Germans, and the chamber was wrecked by a countermine.
The largest of the 21 Messines mines was at Spanbroekmolen; the "Lone Tree Crater" formed by the blast was approximately 250 feet (80 m) in diameter, and 40 feet (12 m) deep. The mine consisted of 41 tons of ammonal explosive, located in a chamber dug 88 feet (27 m) below ground.
The evening before the attack, General Plumer remarked to his staff, "Gentlemen, we may not make history tomorrow, but we shall certainly change the geography."
