As soon as the retreat of the enemy was known, the allied army was put in motion to follow him; his movement was, however, so rapid, that he was not overtaken till within a few miles of Santarem. The rear guard was pushed over the bridge in front of that place, where it took up a strong and formidable position. Lord Wellington had not pursued the enemy with the whole of his force; suspecting, that it might, in the first instance, be the intention of Massena to move round Monte Junto, he retained Major General Picton’s division in its position at Torres Vedras; he afterwards detached Lieutenant General Hill with the corps under his orders across the Tagus at Valada, with a view of communicating with Abrantes, which it might be the intention of the French to attack, and also to protect the Alemtejo from any offensive operation. The rest of the army was brought opposite to Santarem. Lord Wellington having received a report from Major General Fane, that the baggage of the French army was retiring towards Thomar, conceived that Massena was altogether falling back; with this idea he determined to attack what appeared to be his rear guard, which was placed upon a small river, the Rio Mayor. A disposition with this view was made; a part of Brigadier General Pack’s brigade was to have passed, supported by a detachment of cavalry, on the right of the French position, about a mile beyond it; Sir William Erskine’s brigade, supported by the Guards, was to have stormed the bridge; while Major General Crawford, with the light division, was to have attacked the enemy’s left, and along the Tagus to have menaced the rear of his advanced position. The rain, which had been very heavy during the preceding days, had, however, so much swelled the river where Brigadier General Pack was to have passed, that it was found impracticable; the enemy also appearing in considerable force, the operation was given up; Lord Wellington still determining to adhere to his defensive system, and deciding rather to fall back again upon his lines than seek the French army, or give it an opportunity of meeting him upon any thing like equal terms.