Haig developed a concept of all-arms units of "cavalry and mobile troops" to capture a portion of the German defences and enlarge the foothold for later exploitation.

There was some uncertainty over the role of the army, Kiggell, the BEF Chief of Staff writing on 4 June, "The area in which the Reserve Corps (sic) may be employed must be dependent on events and cannot be foreseen".

Sheffield wrote that the all-arms concept was an imaginative response to the tactical problems of 1915 and anticipated post-war moves towards mobile warfare, but was ambitious, and the staff work and traffic control required to make it work, would have been a great burden on the inexperienced armies and staffs of 1916.

"Gough's Mobile Army" was then made ineffective by a disagreement between Haig and Rawlinson about the plan for the Battle of the Somme, Rawlinson wanting to conduct a series of limited advances onto commanding ground, from which German counter-attacks would be smashed.

The intelligence picture led Haig to believe that a more ambitious attack could succeed and he insisted on deeper objectives being substituted for the relatively shallow penetration of the German first position preferred by Rawlinson.

II Corps with the 23rd and 38th divisions, was to be ready to move forward into the vacated assembly areas.