 The attacking corps organised their heavy artillery within the army plan according to local conditions . II Anzac Corps created four counter @-@ battery groups , each with one heavy artillery group and IX Corps arranged four similar groups and five bombardment groups , one for each of the three IX Corps divisions making the initial attack and two ( with the heaviest howitzers ) in reserve , under the control of the corps heavy artillery commander . A Heavy Artillery Group Commander was attached to each divisional artillery headquarters , to command the heavy artillery once the infantry attack began . Field artillery arrangements within corps also varied , in IX Corps groups and sub @-@ groups were formed so that infantry brigades had an artillery liaison officer and two sub @-@ groups , one with six 18 @-@ pounder batteries and one with six 4 @.@ 5 @-@ inch howitzer batteries . Surplus field artillery brigade headquarters planned forward moves for the guns and were kept ready to replace casualties . It was expected that much of the artillery would need to switch rapidly from the bombardment plan to engage counter @-@ attacking German infantry . It was planned that the Forward Observation Officers of the divisions in the first attack onto the ridge would control the artillery which had remained in place and the reserve divisions advancing down the far slope to the Oosttaverne line would control the artillery hidden close to the front line and the artillery which advanced into no @-@ man 's @-@ land . 
