p 86 of Hart's THE SOMME "The importance of the counter-battery role in destroying or subduing the German guns was frequently demonstrated when they opened up in retaliation. Every German shell that landed was a reminder of the destructive power that any surviving German batteries would have if they had not been dealt with before the moment the infantry went over the top."

My understanding was that the allied bombardment concentrated on the various trench lines and not the German guns. However even if the Allies had concentrated some of the artillery fire on the German artillery, then the counter offensive shelling by the Germans was a warning that Germans guns had not been silenced.

This just doesnt sit well with me - men under orders to walk across NML at Zero hour - and I need to give this part of the battle (the artillery preparation) greater study and consideration.