Briefly the artillery plan was as follows: The barrage was organised in depth in four zones.
First came the main creeping barrage. This was fired by the 18-pounder batteries of the 255th, 256th, 58th and 59th Brigades, R.F.A., and advanced at the rate of 50 yards every two minutes for the first 200 yards, every three minutes up to the first objective, and finally 50 yards every four minutes up to the Blue line. In other words, the maximum average rate at which the infantry following the barrage could advance was 1500 yards per hour, the minimum 720 yards per hour—a cold-blooded operation which allows plenty of time for reflection.
The 18-pounders of two further brigades of artillery fired a creeping barrage 100 yards beyond the main barrage.
When the first objective had been captured, a pause in the advance of an hour was arranged, to allow time for cleaning up any pockets of the enemy still holding out, and for the troops for the final objective to move forward and deploy behind the barrage before it moved on. During this pause the No. 3 guns of each battery fired smoke shells, so that a screen of smoke was provided which concealed the infantry from the enemy’s view.[9]
Two hundred yards beyond the creeping barrage came the combing barrage. This was composed of all the 18-pounder batteries of the 65th Brigade Army field artillery, while a further 300 yards beyond all the howitzer batteries of the artillery at the disposal of the Division were employed. The combing barrage dwelt on all “pill-boxes,” strong posts, &c., and also worked up and down the communication trenches.
Beyond the combing barrage was a neutralising barrage of 6-inch howitzers and 60-pounder guns, which also dwelt on pill-boxes, &c.
Finally, there was a standing barrage of heavy howitzers and 60-pounder guns, which dwelt on avenues of approach or likely places for assembly of the enemy’s reserves. As the infantry advanced the whole of these different barrages advanced also, so that by the time the infantry reached the Germans the latter had had during the morning a good sample of most of the types of shells employed by the British artillery.
Altogether this one brigade of infantry was supported by (a) twenty-two 18-pounder batteries, which fired 67,000 rounds on the day of the attack and the same number on the following day; (b) six 4·5 howitzer batteries, which fired 14,000 rounds on the day of the attack and the same number on the following day; (c) twelve batteries of 6-inch howitzers, which fired 5551 rounds during the first four and a half hours of the attack; (d) the following batteries of heavy guns, which fired in the first four and a half hours the ammunition as stated:—
| One battery 6-inch Mark VII. guns | 114 | rounds. |
| One battery 8-inch howitzers | 114 | „ |
| One battery 9·2 guns | 49 | „ |
| Three batteries 9·2 howitzers | 685 | „ |
| One 15-inch howitzer | 20 | „ |
In addition, the 2-inch trench-mortar batteries and Stokes mortar batteries all joined in the bombardment, the latter firing 2700 rounds in the initial stages of the attack.