On the 20th Reille’s troops on the heights above Vera and Sarre, being cautiously relieved by Villatte, marched through Cambo towards St. Jean Pied de Port. They were to reach the latter early on the 22d, and on that day also the two divisions of cavalry and the park of artillery were to be concentrated at the same place. D’Erlon with the centre meanwhile still held his positions at Espelette, Ainhoüe or Ainhoa, and Urdax, thus covering and masking the great movements taking place behind. Villatte who including the foreign battalions had eighteen thousand troops on the rolls, furnishing about fifteen thousand sabres and bayonets, remained in observation on the Bidassoa. If threatened by superior forces he was to retire slowly and in mass upon the entrenched camp commenced at Bayonne, yet halting successively on the positions of Bordegain in front of St. Jean de Luz, and on the heights of Bidart in rear of that town. He was especially directed to shew only French troops at the advanced posts, and if the assailants made a point with a small corps, to drive them vigorously over the Bidassoa again. But if the allies should in consequence of Soult’s operations against their right retire, Villatte was to relieve San Sebastian and to follow them briskly by Tolosa. [Sidenote: Soult’s Official Correspondence, MSS.] Rapidity was of vital importance to the French general, but heavy and continued rains swelled the streams, and ruined the roads in the deep country between Bayonne and the hills; the head-quarters, which should have arrived at St. Jean Pied de Port on the 20th, only reached Olhonce, a few miles short of that place, the 21st; and Reille’s troops unable to make way at all by Cambo took the longer road of Bayonne. The cavalry was retarded in like manner, and the whole army, men and horses, were worn down by the severity of the marches. Two days were thus lost, but on the 24th more than sixty thousand fighting men including cavalry national guards and gensd’armes, with sixty-six pieces of artillery, were assembled to force the passes of Roncesvalles and Maya. The main road leading to the former was repaired, three hundred sets of bullocks were provided to draw the guns up the mountain, and the national guards of the frontier on the left were ordered to assemble in the night on the heights of Yropil, to be reinforced on the morning of the 25th by detachments of regular troops with a view to vex and turn the right of the allies which extended to the foundry of Orbaiceta. Such were Soult’s first dispositions, but as mountain warfare is complicated in the extreme, it will be well to consider more in detail the relative positions and objects of the hostile forces and the nature of the country.