The (second position) roughly corresponded to the British black line (second objective) of 31 July, much of which had been captured, except on the Gheluvelt Plateau. The line marked the front of the main battle zone (), which was about deep, behind which was the (third position) and most of the field artillery of the front divisions. In pillboxes of the were the reserve battalions of the front-line regiments. The leading regiment of an division was to advance into the zone of the front division, with its other two regiments moving forward in close support from support and reserve assembly areas, further back in the . divisions were accommodated behind the front line and at the beginning of an attack began their advance to assembly areas in the behind , ready to intervene in the , for (the instant-immediate counter-thrust).