control the battle. In 2009, J. P. Harris wrote that during the seven weeks' battle for control of Delville Wood, the infantry on both sides endured what appeared to be a bloody and frustrating stalemate, which was even worse for the Germans. The greater amount of British artillery and ammunition was directed by RFC artillery-observers in aircraft and balloons, which increased the accuracy of fire despite the frequent rain and mist. German counter-attacks were tactically unwise and exposed German infantry to British fire power regardless of the value of the ground being attacked. In the Fourth Army sector, the Germans counter-attacked seventy times from September against ninety British attacks, many of them near Delville Wood. The British superiority in artillery was often enough to make costly failures of the German efforts and since German troops were relieved less frequently, the constant British bombardments and loss of initiative depressed German morale. 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 The Battle for Longueval and Delville Wood, had started with a charge by the 2nd Indian Cavalry Division between Longueval and High Wood and two weeks after the wood was cleared, tanks went into action for the first time. A number of important tactical lessons were learned from the battle for the village and wood. Night assembly and advances, dawn attacks after short, concentrated artillery barrages for tactical surprise and building defensive lines on the fringes of wooded areas, to avoid tree roots in preventing digging and to keep clear of shells