Over the winter months, the British 170th Tunnelling Company dug several galleries under the German lines at the Hohenzollern Redoubt, which had changed hands several times since September 1915. In February 1916, mining was being conducted at the Quarries and near Fosse 8, where explosions were frequent and were followed by infantry attacks to occupy the near lip and by sapping forward. In March 1916, the west side was held by the British and the east side was still occupied by the Germans, with the front near a new German trench known as the Chord. The Germans had an unobstructed view of the British positions from a slag heap named Fosse 8 and during previous fighting no man's land had become a crater field. On 2 March, four mines (the largest yet sprung by the British) were detonated, followed by a British advance towards the German lines. The 12th Division intended to capture the crater field, gain observation from crater lips over the German defences back to Fosse 8and end the threat of German mine attacks. German counter-attacks drove the British back by 6 March. On 18 March, the Germans surprised the British with five mines. The 37th Brigade was eventually relieved by the 35th Brigade, and by the time that the crater fighting died down, both sides held the near sides of the craters.
