Hamilton’s Portuguese first invested the place on the left bank, and, the 24th of May, General Houston, having five thousand men, invested San Christoval; a flying bridge was then laid down on the Guadiana below the town, and Picton, crossing that river by a ford above, joined Hamilton. Hill commanded the covering army, all the cavalry was pushed forward in observation of Soult, and when intelligence of Drouet’s junction was obtained, two regiments of cavalry and two brigades of infantry, which had been quartered at Coria as posts of communication with Spencer, were called up to reinforce Hill.
Phillipon had during the interval of siege levelled Beresford’s trenches, repaired his own damages, mounted more guns and obtained a small supply of wine and vegetables from the people of Estremadura, who were still awed by the presence of Soult’s army. Within the place all was quiet, the citizens did not now exceed five thousand souls, and many of them were seen, mixed with soldiers, working at the defences; hence, as retrenchments in the castle behind the intended points of attack would have prolonged the siege beyond the calculated period, Lord Wellington to obtain timely notice of such works had a large telescope placed in the tower of La Lyppe near Elvas, by which the interior of the castle could be searched.
In the night of the 29th the engineers broke ground for a false attack, and the following night sixteen hundred workmen, with a covering party of twelve hundred, sunk a parallel against the castle without being discovered; at the same time twelve hundred workmen, covered by a guard of eight hundred, opened a parallel four hundred and fifty yards from San Christoval and seven hundred yards from the bridge-head. On this line, one breaching and two counter batteries were raised against the fort and bridge-head, to prevent a sally from the last point; a fourth battery was also commenced to search the defences of the castle, but the workmen were discovered and a heavy fire struck down many.
On the 31st the attack against the castle, where the soil was soft, advanced rapidly; but Christoval being on a rock, earth had to be brought from the rear and the attack proceeded slowly and with considerable loss. This day the British artillery company came up on mules from Estremos, the engineer hastened his work, and, to save time, prematurely traced a work for fourteen twenty-four pounders with six large howitzers to batter the castle.