To raise the siege it was only necessary to force a way to Oyarzun, a small town about seven or eight miles beyond the Bidassoa, from thence the assailants could march at once upon Passages and upon the Urumea. To gain Oyarzun was therefore the object of the French marshal’s combinations. The royal road led directly to it by the broad valley which separates the Peña de Haya from the Jaizquibel mountain. The latter was on the sea-coast, but the Peña de Haya, commonly called the four-crowned mountain, filled with its dependent ridges all the space between Vera, Lesaca, Irun and Oyarzun. Its staring head bound with a rocky diadem was impassable, but from the bridges of Vera and Lesaca, several roads, one of them not absolutely impracticable for guns, passed over its enormous flanks to Irun at one side and to Oyarzun on the other, falling into the royal road at both places. Soult’s first design was to unite Clauzel’s and D’Erlon’s troops, drive the light division from the heights of Santa Barbara, and then using the bridges of Lesaca and Vera force a passage over the Peña de Haya on the left of its summit, and push the heads of columns towards Oyarzun and the Upper Urumea; meanwhile Reille and Villatte, passing the Bidassoa at Biriatu, were to fight their way also to Oyarzun by the royal road. He foresaw that Wellington might during this time collect his right wing and seek to envelope the French army, or march upon Bayonne; but he thought the general state of his affairs required bold measures, and the progress of the besiegers at San Sebastian soon drove him into action. On the 29th Foy, marching by the road of Lohoussoa, crossed the Nive at Cambo and reached Espelette, leaving behind him six hundred men, and the national guards who were very numerous, with orders to watch the roads and valleys leading upon St. Jean Pied de Port. If pressed by superior forces, this corps of observation was to fall back upon that fortress, and it was supported with a brigade of light cavalry stationed at St. Palais. In the night two of D’Erlon’s divisions were secretly drawn from Ainhoa, Foy continued his march through Espelette, by the bridges of Amotz and Serres to San Jean de Luz, from whence the reserve moved forward, and thus in the morning of the 30th two strong French columns of attack were assembled on the Lower Bidassoa. The first, under Clauzel, consisted of four divisions, furnishing twenty thousand men with twenty pieces of artillery. It was concentrated in the woods behind the Commissary and Bayonette mountains, above Vera. The second, commanded by general Reille, was composed of two divisions and Villatte’s reserve in all eighteen thousand men; but Foy’s division and some light cavalry were in rear ready to augment this column to about twenty-five thousand, and there were thirty-six pieces of artillery and two bridge equipages collected behind the camp of Urogne on the royal road.