The Germans blew a camouflet on 27 July from Paul Stollen, which caused the sympathetic detonation of a French charge of 6.9 tonnes of dynamite and cheddite and injured eleven of their miners. On the night of 13 August the French completed a charge chamber just one metre from Paul Stollen, in which voices were audible with the naked ear. The Germans, however, used a borer to place a 50kg charge, which broke through into the chamber at about 4am. No French were in the chamber at the time, but the shift arriving for work at 7am discovered the debris from the charge and set about clearing it, unaware that an opening had been created between the German and French systems. As they cleared the opening they facilitated the release into their gallery of the poisonous gases produced by the explosion. At this time the French generator broke down, depriving them of both ventilation and lighting and forcing them to withdraw. The Germans noticed the lack of French activity and, fearing a camouflet, also withdrew. However, Staff Sergeant Menges, picking his way in darkness over sandbags brought up for tamping, climbed through the partially blown in opening. At 1pm a shift of four French miners under Sergeant Charbonnier resumed work. The man in front, Sapper Rubbefat, shouted back to Charbonnier that the air was clear. He was then seized by Menges who, firing a shot in the direction of the others, dragged him back to the Paul Stollen. Charbonnier had a pistol but panicked and went back up the gallery, pushing ahead of him the other two. Menges continued his exploration of the French system. Others began to bring in cases of explosives to prepare a charge to seal off the two branches of the D6 gallery from the shaft entrance to prevent the French entering. A French infantry bomber stationed at the entrance of D6 saw down below a man carrying an acetylene light, but took him for a French sapper still in the gallery. A French engineer officer, Lieutenant Pech, descended into the gallery, followed by several men including a bomber. He could not see or hear any sign of the Germans but smelt a strong odour, which he recognized as a slow burning fuse. He immediately evacuated the gallery. Three or four minutes later the German charge blew, hurling sandbags and pieces of wood towards the entrance and blocking the gallery. After the blow, the Germans were able to visit the whole of the system undisturbed, discovering tools and rescue and listening equipment. The French set about bracing adjacent galleries in their X and V systems against an expected German charge, which they could hear being prepared at midnight. The Germans blew a charge of 5 tonnes at 4.30am, which formed a crater above ground.

The French were left without defence between their V and X galleries. The final deep gallery W in this area had been stopped in June owing to lack of labour and bad ground and it would take a month and half to recover the lost ground. They therefore drove a branch from X gallery to the right to extend 50m, and also blew a 6-tonne camouflet on 20 August, which cut the German gallery. The Germans replied on 28 August. The struggle with camouflets continued, particularly in the centre and east sectors, and between February and August 38 German and 47 French charges were blown. The quantity of gas trapped in the workings required an increase in the number of ventilators, which the French reversed to suck rather than blow in order not to force the gas further into the system. In the west, after a heavy German camouflet on 1 September, the French blocked D5 gallery with barbed wire and abandoned it. In October and December 1917 the French engineer companies were again changed, with only M5/T remaining in the east.

During autumn and winter 1917 the French continued to attempt to stabilize the situation without actually giving up the ridge. This was not solely in order to avoid creating a gap in the French line, but also for purposes of morale and, according to a French report, for the sake of the ‘dignity of the French miner’.²² The French pushed their galleries to reach the centre of the craters, but did not go beyond that line so as not to attract German attention. They planned to use a new drilling machine to drive a transversal between Y and Z in the centre-west sector to cover an undefended area. This was one of the few uses by the French at Vauquois of lateral tunnels to link their attack galleries.

At Christmas a remarkable incidence of fraternisation deep underground occurred, which was indicative of the desire by the French to introduce a degree of ‘live and let live’, and also probably war-weariness on the part of miners on both sides. On 17 December French listeners heard working beneath their D3 gallery and began a shaft to meet it. The two galleries reached within a metre of one another and the French heard the Germans addressing them in their own language: ‘If you do not advance any more, we will not advance any more.’ The French listeners were forbidden to reply. A little later, when the French were clearing spoil, they heard ‘Tu travaille?’. The French put a 200kg camouflet and a microphone in place in the gallery face, with which they could hear the Germans speaking and also singing. Corporal Feikert recalled how the Germans broke the truce:

It was around Christmas time. We advanced straight forward, until one day we heard the French speaking in the gallery. We succeeded in making contact and it was genuinely cordial with them. Since we couldn’t understand each other, the French sang the Marseillaise and we the German national anthem. When the French were quiet, we also left the gallery, attaching however listening apparatus at the tunnel entrance for security.

This didn’t please our second lieutenant and he told us to do something. No one volunteered. We were all cowards in his eyes. A pioneer corporal however then came forward with one of my mates (a Saarlander). The pair put in two 25kg boxes of explosive. It was tamped and blown. (Corporal Ludwig Feikert, 399 Pioneer Mining Company)²³