The retirement to the Hindenburg Line took place Process_start as part of the ( Operation Alberich/Alberich Manoeuvre ) from February to March 1917 , after local withdrawals on the Somme had been forced on the 1st Army by British attacks Attack up the Ancre valley in January and February .

The Battle Hostile_encounter of the Ancre was fought Hostile_encounter by the Fifth Army ( Lieutenant-General Hubert Gough ) , against the German 1st Army ( General Fritz von Below ) .

Fricourt formed Creating a salient in the German front-line and was the principal German fortified village between the River Somme and the Ancre .

Nine corps of the French Sixth Army and the British Fourth and Third armies , attacked Attack the German 2nd Army ( General Fritz von Below ) from Foucaucourt south of the Somme northwards across the Ancre to Serre and at Gommecourt , beyond , in the Third Army area .

On the north bank of the Ancre , the attack Attack of VIII Corps was a disaster , with large numbers of British troops being shot down in no man 's land .

The British reopened Openness the tunnel beneath the Hawthorn Ridge crater three days later and reloaded the mine with explosives for the Battle of the Ancre .

Attacked Attack several times by the Canadian Corps during the Battle of the Ancre Heights , the 5th Canadian Brigade of the 2nd Canadian Division briefly controlled Control a section of the trench on 1 October but was repulsed Defending by counter-attacks of the German Marine Brigade ( equivalent to an army division ) , which had been brought Bringing from the Belgian coast .

The redoubt was a German strong point long and wide , built Building in stages since 1915 , near the village of Thiepval , overlooking Perception_active the River Ancre .