The British had begun a mining offensive against the (Wytschaete position) in 1916. Sub-surface conditions were especially complex and separate ground water tables made mining difficult. Two military geologists assisted the miners from March 1916, including Edgeworth David, who planned the system of mines. Sappers dug the tunnels into a layer of blue clay underground, then drifted galleries for to points deep underneath the front position of , despite German counter-mining. German tunnellers came close to several British mine chambers, found the mine at La Petite Douve Farm and wrecked the chamber with a . The British diverted the attention of German miners from their deepest galleries by making many secondary attacks in the upper levels. Co-ordinated by tunnelling companies of the Royal Engineers, Canadian, Australian, New Zealand and British miners laid with of ammonal explosive.