First of all I’ll tell you the first bit of why the British failed to achieve their objectives in the battle of the some it change the state of war and the British learnt there lesion and also broke the stale mate.
The British plan did not quiet go so well. This is because they had failed to break the German line the brutish bombard the German trenches. For a number of months the French had been taking severe losses at Verdun to the east of Paris. To relieve the French the allied high command decided to attack the Germans to the north of Verdun they’re fore requiring the French. The leader of the French army general Foch believed that the attack in the Somme would achieve little.