Battle of Vimy Ridge - Prelude - Underground Operations

Underground Operations

The Arras-Vimy sector was conducive to tunnel excavation owing to the soft, porous yet extremely stable nature of the chalk underground. As a result, pronounced underground warfare had been an active feature of the Vimy sector since 1915. The Bavarian engineers, for example, had blown 20 mines in the sector by March 1915. By early 1916 the German miners had gained a clear advantage over their French counterparts. On their arrival, the British Royal Engineer tunnelling companies became actively engaged in offensive mining against German miners, first stopping the German underground advance and then developing a defensive strategy that prevented the Germans from gaining a tactical advance through their mining activities. By 1917, no fewer than 19 distinct crater groups existed along the section of the front. Each group often contained several large craters all of which were the result of explosions caused by underground mine warfare.

In preparation for the assault, British tunnelling companies created extensive underground networks and fortifications. Twelve subways, up to 1.2 kilometres (1,300 yd) in length, were excavated at a depth of 10 metres (33 ft) and used to connect reserve lines to front lines, permitting soldiers to advance to the front quickly, securely and unseen. Often incorporated into subways were concealed light rail lines, hospitals, command posts, water reservoirs, ammunition stores, mortar and machine gun posts, and communication centres. The Germans dug a number of similar tunnels on the Vimy front to provide covered routes to front lines and large-scale protection for headquarters, resting personnel, equipment and ammunition.

To protect some advancing troops from German machine gun fire as they crossed no man's land during the attack, eight specialized mine charges were laid at the end of the subways. These specialized mine charges were designed to allow troops to move more quickly, and safely enter the German trench system by creating an elongated trench-depth crater that spanned the entire length of no man's land. In an effort to destroy some German surface fortifications before the assault, the British tunnelling companies secretly laid 13 large explosive charges directly under German positions. However, this work did not go unimpeded; the Germans actively counter-mined British tunnelling and were successful in destroying a number of British attempts at placing offensive mines under or near their lines. Of the explosive charges laid by the British, three mines were fired before the assault; another three mines and two specialized charges were fired at the start of the attack.