Royal Engineer tunnelling companies were specialist units of the Corps of Royal Engineers within the British Army, formed to dig attacking tunnels under enemy lines during the First World War. The stalemate situation in the early part of the war led to the deployment of tunnel warfare. After the first German Empire attacks on Monday, 21 December 1914, through shallow tunnels underneath no man's land and exploding ten mines under the trenches of the Indian Sirhind Brigade, the British began forming suitable units. In February 1915, eight Tunnelling Companies were created and operational in Flanders from March 1915. By mid-1916, the British Army had around 25,000 trained tunnellers, mostly volunteers taken from coal mining communities. Almost twice that number of "attached infantry" worked p