The 17th, the eighth corps marched upon Alcanhede and Pernes, the head of the second corps reached Santarem, and Fane, deceived by some false movements, reported that they were in full retreat, and the troops at Santarem only a rear guard. This information seeming to be confirmed by the state of the immense plains skirting the Tagus, which were left covered with straw-ricks, it was concluded that Massena intended to pass the Zezere, over which it was known that he had cast a second bridge. Hill was immediately ordered to cross the Tagus with the second division and thirteenth dragoons, and move upon Abrantes, either to succour that fortress or to head the march of the French. Meanwhile, the fourth, fifth, and sixth divisions were directed upon Alemquer, the first division and Pack’s brigades upon Cartaxo, and the light division reached El Valle, a village on the Rio Mayor, where a considerable rear guard was formed, and an unequal engagement would have ensued, but for the opportune arrival of the commander-in-chief. In the evening the enemy joined their main body on the heights of Santarem. Hitherto, lord Wellington, regarding the security of the Lines with a jealous eye, acted very cautiously. On the 15th and 16th, while the French were still hampered by the defiles, his pursuit was slack, although it would in no degree have risked the safety of the Lines, or of the pursuing troops, to have pushed the first, second, and light divisions and Pack’s brigade vigorously against the enemy’s rear. On the 18th, however, when Hill had passed the Tagus at Villada, and Fane was opposite to Abrantes, lord Wellington, whether deceived by false reports, or elated at this retrograde movement, this proof of his own superior sagacity, prepared, with a small force, to assail what he conceived the rear guard of an army in full retreat. But the French general had no intention of falling back any farther; his great qualities were roused by the difficulty of his situation, he had carried off his army with admirable arrangement, and his new position was chosen with equal sagacity and resolution. Santarem is situated on a mountain, which, rising almost precipitously from the Tagus, extends about three miles inland. In front, a secondary range of hills formed an outwork, covered by the Rio Mayor, which is composed of two streams, running side by side to within a mile of the Tagus, but there they unite and flow in a direction parallel with that river for many miles; the ground between being an immense flat, called the plain of Santarem.