On finding that the Portuguese were determined to fight, Soult began his preparations for a general assault upon the following day. He drove in the enemy’s outposts outside the town, and captured one or two small redoubts in front of the main line. Having reconnoitred the whole position, he told off Delaborde and Franceschi to attack the north-eastern front, Mermet and one brigade of Lahoussaye’s dragoons to storm the central parts of the lines, due north of the city, where the fortifications were most formidable, Merle and the other brigade of Lahoussaye to press in upon the western entrenchments below the city. There was no general reserve save Lorges’ two regiments of cavalry, and these had the additional task imposed upon them of fending off any attack on the rear of the army which might be made by scattered bodies of _Ordenanza_, who were creeping out into the woods along the sea-coast, and threatening to turn the Marshal’s right flank.
Soult had but 16,000 men available,--of whom 3,000 were cavalry, and therefore could not be employed till the infantry should have broken through the line of fortifications which completely covered the Portuguese front. Nevertheless he had no doubts of the result, though he had to storm works defended by 30,000 men and lined with 197 cannon. He now knew the exact fighting value of the Portuguese levies, and looked upon Oporto as his own.
The Marshal’s plan was not to repeat the simple and simultaneous frontal attack all along the line by which he had carried the day at Braga. There was a good deal of strategy in his design: the two flank divisions were ordered to attack, while the centre was for a time held back. Merle, in especial, was directed to do all that he could against the weakest point of the Portuguese line, in the comparatively level ground to the west of the city. Soult hoped that a heavy attack in this direction would lead the enemy to reinforce his left from the reserves of his centre, and gradually to disgarnish the formidable positions north of the city, when no attack was made on them. If they committed this fault, he intended to hurl Mermet’s division, which he carefully placed under cover till the critical moment, at the central redoubts. A successful assault at this point would finish the game, as it would cut the Portuguese line in two, and allow the troops to enter the upper quarters of the city in their first rush.