The Germans blew the charge on 29 December, gassing two French sappers.

At the end of February 1918, in the expectation of a German offensive on the western front, preparations were put in hand by the French engineers to destroy the underground workings should the ridge be abandoned by their forces. The Germans continued to advance underground and, at the beginning of 1918, their three deepest galleries had reached 95, 94 and 92m depth and remained undiscovered by the French. They began a chamber at the end of Mittel Stollen capable of taking a charge of 200 tonnes. The French, however, believed that there were signs that the Germans were also becoming less aggressive and looking to stabilize the situation. When the Germans blew a camouflet in February they then halted their gallery, timbered the face and installed a listening post. In the month of March 1918 they blew just one camouflet. After the launch of the German offensive on 21 March an attack on Vauquois seemed unlikely. On that day the French blew 3 tonnes of cheddite, which was to be their last camouflet at Vauquois. At the end of March the German pioneers were ordered to cease work in the deep galleries, but to blow on 9 April against the French Y attack gallery and to answer the French blow of 21 March. This camouflet, which destroyed two French galleries, was to be the last at Vauquois. The 1/Pi 30 left Vauquois on 18 April after three years and four months on the ridge and its place was taken by 399 and 412 Pioneer Mining Companies. The French recovered their galleries and continued maintenance. Their listening revealed almost no German activity in the east and west. They put seismomicrophones in the ends of their galleries, with charges of 100kg for contingencies. On 16 May Italian troops relieved the French on Vauquois, who left some engineer units. On 2 June the French began to remove their mining plant from the galleries, which they blocked with barbed wire and sandbag barricades. The deeper galleries quickly flooded after the pumps were removed. The listening devices were left in place, with the last report recorded on 22 June. Some galleries were left with charges in place, several of which remain to this day.

The German Vauquois position, where previously infantry were packed densely into the forward positions in underground shelters, was superseded by changes in defensive tactics in which the main forces were held further back. By 1 January 1918 the main line of resistance in the sector was through Varennes and Cheppy 1.5 miles in the rear. Vauquois was in the outpost zone, which would normally be expected to delay an advance while counterattack forces were mustered. The ridge, however, was not to be abandoned if attacked but held as a ‘closed work’, and the garrison was reported to have been equipped to hold it even though it was completely isolated. When Vauquois fell to the Allies on 26 September 1918, in the first phase of the Meuse-Argonne offensive, the garrison had been greatly reduced. The US 35th Division was supported by massive quantities of artillery and tanks and was aided by fog and smoke. Its troops bypassed and surrounded the ridge, which fell after some fierce but brief resistance. Mining played no part in the assault and little part in the defence.

The Germans maintained the initiative and supremacy underground at Vauquois during 1915-1918. Their position was potentially difficult as they held just 50m width of the plateau, which then fell steeply away in the northern slope. All their defences had to be squeezed into this small area and they dug extensive accommodation for an infantry garrison. They also turned the rear slope to their advantage, for it enabled them to drive only slightly inclined or even straight tunnels into the side of the hill, which were already beneath those shafts sunk by the French from their front lines. They could also easily evacuate the spoil by tipping it over the side. These mine entrances were impossible for the French to observe, except by aircraft, or to bombard. The more gentle slope behind the French position was less useful in this respect and it took the French longer to make use of this method of driving inclined galleries, which on their side had to be longer and more steeply sloped. The Germans also benefited from keeping the same pioneer unit in place at Vauquois for the whole of the active mining period, so that experience was gained in working the particular geology of the ridge and an intimate knowledge of the location and working habits of the French miners was acquired. The 1/Pi 30 was supplemented at Vauquois by infantry mining companies, for example Stollenbaukompanie (Tunnelling Company) 1, formed from the 98th Infantry Regiment, and Stollenbaukompanie 2 from the 130th. In April 1917 these were converted into 398 and 399 Pioneer Mining Companies.²⁴ The Germans were less hampered by a shortage of personnel, but seem to have more quickly mechanized their mining at Vauquois.

Both Vauquois and Les Éparges were active mining areas owing to their value as important observation posts. They also were heavily fought over for doctrinal reasons. The Germans, until 1916, defended their front lines tenaciously and held large numbers of men in or immediately behind it for that purpose. The French made extremely costly attacks to recover the smallest villages from German hands. Both sides, however, considered withdrawal from Vauquois. The French wished to disengage from mining as not worth the effort and a war that they were not winning, but found it difficult to do so without wholly giving up the position. Ultimately it was the change in German defensive doctrine which was the deciding factor in mining coming to an end at Vauquois. By the time of the capture of Vauquois by the US 35th Division the ridge was, in effect, an outpost of the main defence line and was enveloped by a tank advance.