During the night of the 16-17th Divisional headquarters opened at Moussy, three miles south-west of Epernay. On the following day the enemy continued his advance north and south of the Marne, and had also further encroached on the Montagne de Rheims, his farthest point of penetration in the Epernay area being Boursault, a village four and a half miles north-west of Moussy on the other side of the forest of Epernay. During the night of the 17th the 152nd, 153rd, and 154th Brigades established their headquarters at Le Mesnil, Pierry, and Chouilly respectively, the infantry battalions, now almost complete, being grouped in villages and woods about their brigade headquarters. Regimental transport, field companies, and field ambulances, which were marching from their detraining stations, had not yet arrived in their brigade group area, the first being still many miles behind, while the Divisional artillery was still detraining during the day. On 18th July Marshal Foch opened his counter-offensive on the western flank of the Rheims-Soissons salient, which, with a series of counter-attacks delivered south of the Marne, arrested the enemy's advance. While these operations were in progress, the Divisional artillery were on the march from their detraining station, Nogent-sur-Seine, and the bulk of the regimental transport, field ambulances, and field companies were arriving in their brigade group areas. During the night 18-19th July the original plan of employing the Division south of the Marne was changed, and orders were received at 1 A.M. for it to move to the Forêt de la Montagne de Rheims. This move was carried out on the morning of the 19th, the troops crossing the Maine at Epernay and moving to the south-western fringe of the Forêt de la Montague. By 9 A.M. Divisional headquarters had been established at Hautvillers, 152nd Brigade headquarters at Champillon, 153rd Brigade headquarters at Romery, and 154th Brigade in woods one mile north of Bellevue. The Divisional artillery had also concentrated on the Moussy-Pierry area. All these moves were carried out in a hilly country in days of intense heat, broken on the 18th by a violent thunderstorm, and proved extremely trying both to men and horses--to the former particularly after nine weeks of continual trench warfare. The Divisional artillery had covered eighty miles in three days by forced marches, and after the storm on the 18th had found the roads impassable in many places owing to trees which had been blown down in the storm and which had to be cleared before the batteries could pass on.