 Two thirds of the 18 @-@ pounders were to fire a creeping barrage of shrapnel immediately ahead of the advance , while the remainder of the field guns and 4 @.@ 5 @-@ inch howitzers were to fire a standing barrage , 700 yards ( 640 m ) further ahead on German positions and lift to the next target , when the infantry came within 400 yards ( 370 m ) of the barrage . Each division was given four extra batteries of field artillery , which could be withdrawn from the barrage at the divisional commander 's discretion to engage local targets . The field batteries of the three reserve divisions were placed in camouflaged positions , close to the British front line . As each objective was taken by the infantry , the creeping barrage was to pause 150 – 300 yards ( 140 – 270 m ) ahead and become a standing barrage , while the infantry consolidated . During this time the pace of fire was to slacken to one round per @-@ gun per @-@ minute , allowing the gun @-@ crews a respite , before resuming full intensity as the barrage moved on . The heavy and super @-@ heavy artillery was to fire on German artillery positions and rear areas and 700 machine @-@ guns were to fire a barrage over the heads of the advancing troops . 
