From April to July, the aims were to deepen defences east of Hébuterne, push out further from the shell-trap of Rossignol Wood and secure a better field of fire and wider observation over the Puisieux valley. The German's withdrawal towards Puisieux in August, was now made a matter of urgency by their defeat in the Battle of Amiens (8th-12th August). To economise man-power and build up reserves, Dudendorff decided to straighten and shorten his line by withdrawing from such awkward salients as at Serre.
In the first week of August the enemy's outposts had begun to retire on the Lys salient about the Division's old rest areas at Vieux Berquin, and on the night 13th/14th August, after leaving booby-traps and filling dugouts with mustard gas and ineffectively mining them, he began to fall back from the network of trenches west of Serre.
The Allies took the opportunity to push forward and by the 16th of August, 1st Auckland, under cover of a light trench mortar barrage cleared Fork Wood and Crayfish as far as the Divisional boundary at the railway siding in the valley, and in conjunction with 2nd Wellington developed their line of outposts on the Bucquoy road.
This trench map provides an insight into why the German defense was respected and the five months spent moving 3-4 miles.