 Large numbers of posts , from which machine @-@ guns were to fire an overhead barrage were built and protective pits were dug for mules , which were to carry loads of 2 @,@ 000 rounds of ammunition to advanced troops . Three field companies of engineers with a pioneer battalion were kept in reserve , to follow up the attacking infantry and rebuild roads and work on defensive positions as ground was consolidated . The artillery in support of the division devised a creeping and standing barrage plan and time @-@ table , tailored to the estimated rates of advance of the infantry units . The standing barrage lifts were to keep all trenches within 1 @,@ 500 yards ( 1 @,@ 400 m ) of the infantry under continuous fire and targets fired on by 4 @.@ 5 @-@ inch howitzer , 6 @-@ inch howitzer and 8 @-@ inch howitzers were to change from them only when infantry got within 300 yards ( 270 m ) . The 18 @-@ pounder field gun standing barrages would then jump over the creeping barrages , to the next series of objectives . The concealed guns of the Guards Division field artillery were to join the creeping barrage for the advance at 4 : 50 a.m. and at 7 : 00 a.m. the 112th Army Field Brigade was to advance to the old front line , to be ready for an anticipated German counter @-@ attack by 11 : 00 a.m. 
