Hereabouts the river system is somewhat intricate, no fewer than five considerable streams flowing, in almost parallel channels, from south to north. On the east the Agueda flows close by the walls of Ciudad Rodrigo; westward of the Agueda are its tributaries, the Azava, the Duas Casas, and the Turon; and a little to the west of Almeida is the Coa—all within a space of thirty miles, and for the most part unfordable. As early as the 24th April Massena had pushed forward his advanced troops from Ciudad Rodrigo, with the object of seizing the crossings of the Azava, but the British outposts on that river drove them back, and continued to hold the river line, until Wellington arrived and selected a position behind the Duas Casas, when the outposts gradually fell back and allowed the French to advance. This they did on the 2nd May, and, on the 3rd, succeeded in crossing the Duas Casas at one point and capturing the village of Fuentes. They did not, however, remain long in possession, for after a fierce fight the British drove them out and forced them back across the Duas Casas.

Next day, Massena moved forward with 5000 cavalry and 40,000 infantry, and Wellington made some alterations in his dispositions, so that his front now extended for a distance of some seven miles. By this new arrangement, the 7th Division (to which the 51st belonged) was placed on the extreme right, near the hill of Nava de Avel, opposite to which the French appeared to be massing in strength. On the morning of the 5th May Massena pushed on, and simultaneously attacked the village of Fuentes and the right of the British position. The 7th Division, outnumbered, were forced back, but the Light Division and the cavalry hastened to its support, and restored the fight. Wellington, now observing that his right was in imminent danger of being turned, ordered the 7th Division to draw in, and the Light Division covered the withdrawal in a magnificent manner. The enemy's strong force of cavalry made strenuous efforts to crush this portion of the line, and what immediately occurred is best described in the words of Napier. "The Light Division," he says, "was thrown into squares; the Seventh Division, which was more advanced, endeavoured to do the same, but the horsemen were too quick upon them, and some were cut down; the remainder stood firm, and the Chasseurs Britannique ranged behind a loose stone wall poured such a fire that the French recoiled and seemed bewildered."

According to all accounts, the battle scene at this phase of the fight was a most picturesque one. The vast plain was covered with charging bodies of horsemen, who once and again endeavoured to break the squares, which, nothing daunted, met the onslaught, and leisurely retired. But the grandest sight of all on that memorable day was perhaps that presented by Norman Ramsay's two-horse artillery guns, which, hemmed in and cut off by the enemy's cavalry, saved themselves, not by their fire, but by cleaving their way at full gallop through the astonished French horsemen. This was, however, but one incident of many in a day of great deeds, and for a long while the issue of the fight hung in the balance. Failing to effect his purpose on the British right, Massena directed his attention to the capture of the village of Fuentes; but at this point also his troops were eventually beaten back, and at nightfall the British and French sentries, separated only by the breadth of the Duas Casas, agreed to take water from the river without molestation—a tacit agreement which always existed in Peninsular warfare between the veterans of the opposing armies.

Considering the critical situation in which the 7th Division was for so long placed, the casualties in the 51st on this day were remarkably few—only half a dozen wounded. In the briefest of letters Sam Rice described the events in which he had taken part as senior major of the regiment. "We have suffered little," he wrote, "though the first attack was made on our regiment by a body of cavalry, who came up to the charge, but were soon convinced that we were not to be trifled with. I am well and safe. I had an 'all-but,' having my cap whisked off by a three-pounder, but received no other injury than a temporary stunning from the concussion. The French again menaced us this morning, but it has since proved a mere manœuvre, and they are off, and we prepared to follow. I literally have not time to say more."

This was written on the day after the battle, and it is possible that the writer was too sick at heart to say more; for something had occurred, as will be disclosed a little later on, which must have caused endless regret to every officer of the regiment who came out of action. They were not, however, given much time to brood over their misfortune, for on the 10th May Massena gave up the attempt to reach Almeida, and withdrew his army beyond the Agueda, when he was relieved of his command by Marmont. That same night, Brenier, in command of Almeida, seeing that there was now no hope of succour reaching him, resolved on a bold stroke. Having destroyed the guns of the fortress, he marshalled the garrison, and, in one solid mass, at dead of night, broke through the blockading force, almost before any one was aware of what was taking place, and eventually made his escape with only a few casualties. Wellington, disgusted at the escape of the garrison, vented his wrath on his lax troops in no measured terms, and leaving Sir Brent Spencer with a sufficient force to watch Marmont, despatched the remainder of the army to Badajoz, the siege of which he proposed to renew at once.

While Wellington was fighting Massena at Fuentes d'Onor, much had been going on in the neighbourhood of Badajoz, and Wellington, although seemingly so fully occupied in the north, was at the same time planning for the overthrow of Soult in the south. It will be remembered that when he hurriedly left Badajoz, at the end of April, to attend to Massena, he instructed Beresford to prosecute the siege leisurely. Certainly Beresford could do no more, since, as has been said, he lacked all the requisites for a regular siege, but he attempted more, and failed ignominiously. From the 5th to the 12th May the first siege of Badajoz was carried on without sufficient organisation, and assaults were directed on various points before they had been properly breached, with the result that within the week Beresford had lost nearly a thousand men, and had made no impression on the fortress. Then came the news that Soult was moving to the relief of the garrison, when Beresford at once raised the siege, marched south, and prepared to give battle. On the 16th May was fought the memorable and bloody battle of Albuhera (or Albuera), where, more by good luck than good management, Beresford, with a loss of four thousand of his eight thousand men, succeeded in defeating his adversary, whose losses were still heavier. The investment of Badajoz was now resumed, and Wellington was soon on the spot, making arrangements for a second siege.

Badajoz at this time was probably the strongest fortress on the Spanish frontier. It was situated on the south bank of the Guadiana, a broad and deep river, which was of itself considered to be sufficient protection from an attack from the north. On that side, therefore, the defences of the fortress consisted only of a simple rampart. On all other sides the fortifications were formidable, having regular bastioned fronts, with solid masonry parapets, encircled by a ditch in places thirty feet deep. Within the north-east angle of the fortress stood the ancient castle, built on a hillock one hundred feet in height, and overlooking the Guadiana; yet, in its turn, overlooked by the high ground (barely five hundred yards distant) to the north of the river. In order to guard against the possibility of an enemy's artillery occupying these heights and demolishing the castle, a detached fort, known as St Christoval (or San Christobal), had been built on them; while, on the opposite side of Badajoz, there were two detached works—Pardeleras on the south, and Picurina on the south-east.

In the first siege, Beresford had attempted to attack from the north, capture St Christoval, and, after establishing batteries, breach and assault the castle. St Christoval, however, proved too strong for the assailants, and thus Beresford was forced to leave his work undone. When Wellington came on the scene to prepare for the second siege, he decided to follow Beresford's plan, and accordingly, on the 24th May, the 7th Division invested St Christoval. Trenches were now commenced towards the castle and towards St Christoval, and batteries were soon erected. During the first few days of June the trenchwork made rapid progress, and the guns fired continuously on the castle and on the fort. On the 6th June, a practicable breach in St Christoval was reported, and the assault was ordered to take place forthwith.

On the night of the 6th-7th, the assault was launched, Major Macintosh, of the 85th, commanding the Stormers, and Ensign Dyas, of the 51st, the Forlorn Hope. The advanced party succeeded in dropping into the ditch undiscovered, and the Stormers with their escalading ladders followed close behind, but on reaching the breach it was found that the defenders had succeeded in repairing it, and had added to its summit a high perpendicular wall—so high that the ladders would not nearly reach the top. Then the enemy's musket-fire fell upon the unfortunate Stormers, and shells, rolled from the ramparts, bursting amongst them, played havoc in the ranks. Retreat was inevitable, and upwards of a hundred dead and wounded were left in the ditch.