Lanrezac had always anticipated the northern attack, and had made representations on the subject without effect.[22] At last, on August 16, General Joffre, from his headquarters at Vitry-le-François, in southern Champagne, agreed to his request that he should move the 5th Army north-westward into the angle of the Sambre and Meuse. At the same time, however, its composition was radically upset, the 11th Corps and two reserve divisions being sent to the 4th Army, while the 18th Corps and the Algerian divisions were received in compensation. On August 16, the British Commander-in-Chief, after seeing President Poincaré and the Ministers in Paris, visited the Generalissimo at Vitry; and it was arranged that the Expeditionary Force, which was then gathering south of Maubeuge, should move north to the Sambre, and thence to the region of Mons. On the same day, General d’Amade was instructed to proceed from Lyons to Arras, there to gather together three Territorial divisions of the north which, reinforced by another on the 21st and by two reserve divisions on the 25th, ultimately became part of the Army of the Somme. Had there been, on the French side, any proper appreciation of the value of field-works, it might, perhaps, not have been too late to defend the line of the Sambre and Meuse. It was four or five days too late to attempt a Franco-British offensive beyond the Sambre. To do justice to the Allied commanders, it must be kept clearly in mind that they had (albeit largely by their own fault) but the vaguest notion of what was impending. Would the mass of the enemy come by the east or the west of the Meuse, by the Ardennes or by Flanders, and in what strength? Still sceptical as to a wide enveloping movement, Joffre was reluctant to adventure too far north with his unready left wing; but it seemed to him that, in either case, the intended offensive of the French central armies (the 3rd and 4th) across the Ardennes and Luxembourg frontier might be supported by an attack by Lanrezac and the British upon the flank of the German western armies——the right flank, if they passed by the Ardennes only; the left, if they attempted to cross the Flanders plain toward the Channel. Thus, it was provisionally arranged with the British Commander that, when the concentration of the Expeditionary Force was complete, which would not be before the evening of August 21, it should advance north of the Sambre in the general direction of Nivelles (20 miles north-east of Mons, and half-way between Charleroi and Brussels). If the common movement were directed due north, the British would advance on the left of the 5th Army; if to the north-east or east, they would be in echelon on its left-rear. General Joffre recognised that the plan was only provisional, it being impossible to define the projected manœuvre more precisely till all was ready on August 21, or till the enemy revealed his intentions.