An unusually large amount rain in August, poor drainage and lack of evaporation turned the ground into a morass, which was worse for the British and French, who occupied lower-lying ground and attacked areas which had been frequently and severely bombarded. Mud and flooded shell holes severely reduced the mobility of the infantry and poor visibility hampered artillery observers and artillery-observation aircraft. Rainstorms and the costly German defensive success during the rest of August, led the British to stop the offensive for three weeks.