By the end of July, the German defence north of the Somme had reached a point of almost permanent collapse; on 23 July, the defence of Guillemont, Delville Wood and Longueval almost failed and from 27 to 28 July, contact with the defenders of the wood was lost; on 30 July another crisis occurred between Guillemont and Longueval. Inside the flanks of the German first position, troops occupied shell-holes to evade bombardment by the British artillery, which vastly increased the strain on the health and morale of the troops, isolated them from command, made it difficult to provide supplies and to remove wounded. Corpses strewed the landscape, fouled the air and reduced men's appetites even when cooked food could be brought from the rear; troops in the most advanced positions lived on tinned food and went thirsty. From 15 to 27 July, the 7th and 8th divisions of IV Corps, from Delville Wood to Bazentin le Petit suffered