On 18 March, the Germans surprised the British with five mines, which had been quietly dug through the clay layer above the chalk. The German attack had nearly as much success as the British attack on 2 March and forced back the British to the original front line, before local counter-attacks regained some of the craters. When the fighting died down after 19 March, both sides occupied the near lips of the craters. Brigadier-General Cator, the 37th Brigade commander, recommended that attempts to occupy craters should end and the near lips be held instead, because they were death traps against howitzer and mortar fire and because the expected observation from the crater lip, was obstructed by its convex shape and large lumps of chalk brought to the surface by the explosions.