After withdrawing from before Ciudad Rodrigo, the regiment was allowed only a short period of repose before it was called upon to march to Spanish Estremadura, to take part in wresting the strong fortress of Badajoz from the enemy. Leaving its cantonments near Fuentes d'Onor on the 27th of February, it proceeded southwards; boats were laid over the Guadiana on the 15th of March, and on the following day Badajoz was invested by the third, fourth, and light divisions; the Royal Fusiliers, forming part of the fourth division, were engaged in the siege. The batteries were opened, and, notwithstanding the sallies of the French garrison under the resolute General Phillipon, inundations from heavy rains, and other obstructions, practicable breaches were ready in the early part of April; and on the evening of the 6th of that month the Royal Fusiliers were under arms to take part in the storming of that stupendous fortress. The fourth and light divisions were to march against the breaches; the light division was to assault the bastion of Santa Maria, and the fourth, the Trinidad, with the breach in the curtain connecting the two bastions; one body of the grenadiers of the fourth division, under Captain John Mair, of the Royal Fusiliers, led the attack against the bastion of Trinidad; and another body, under Captain William Francis Cholwick, also of the Seventh, led the assault on the breach in the curtain.
Moving silently from their camp-ground along the left of the river Rivillas and the inundations, the fourth and light divisions made a short detour, and arrived at the glacis at the moment the third division attacked the castle. Ladders were placed, and about five hundred men of the light division had descended into the ditch with the most heroic bravery, cheering as they went, when suddenly a loud report like thunder was heard, and the storming parties were blown to pieces by the explosion of hundreds of shells and powder barrels. Undismayed by this terrific destruction, the men of the light and fourth divisions raised a loud shout and plunged into the ditch, where many men perished in the inundations; others, after overcoming numerous difficulties, approached the breach exposed to a most destructive fire. As they ascended, loose planks studded with sharp iron points wounded their feet and produced great mischief, and a range of sword-blades with sharp points and keen-edges, firmly fixed in beams chained together and set deep in the ruins, arrested the progress of the soldiers; at the same time a terrible fire of musketry thinned their ranks. Again the assailants rushed up the breaches with the most determined resolution; but the sword-blades stopped their career, and the thundering powder-barrels and hissing shells exploded continually. Numerous and astonishing efforts of valour and intrepidity were made, and the most heroic bravery displayed, yet the obstacles were such as could not be overcome; and about midnight, when two thousand brave soldiers had fallen, the survivors received orders to retire, and re-form for a second attack. In the meantime the third division had captured the castle, and a brigade had carried the bastion of San Vincente; the town was thus forced; partial actions afterwards took place in various places; and the governor escaped to the fort of St. Christoval, where he surrendered. Thus, by the union of ability, energy, and valour, two important fortresses were captured in three months, in the face of two French armies: the British commander was enabled to enlarge the sphere of his operations, and these successes appeared as the first rays of the coming glory which was about to shine resplendently on the British arms.
The Royal Fusiliers were subsequently honoured with the royal authority to bear the word "Badajoz" on their colours; Lieutenant-Colonel Blakeney and Captain John Mair received medals; but the regiment had to regret the loss of many brave men; the casualties among the officers were so great that the command of the division devolved on a major, all the general officers and lieutenant-colonels being wounded. The loss of the Seventh may be seen in the following returns.
List of the Officers of the Royal Fusiliers at the siege of Badajoz.
| Lieutenant-Colonel Edward Blakeney, wounded. | Lieutenant | Paul St. Paul, killed. | |
| Major James Singer, killed. | " | T. Moses, wounded. | |
| Captain | Wm. F. Cholwick, killed. | " | A. Baldwin, wounded. |
| " | George King. | " | James Anderson. |
| " | A. C. Wylly. | " | H. F. Devey, wounded. |
| " | John Mair, wounded. | " | G. Henry, wounded. |
| " | W. M. Hamerton. | " | Pitt Hannam. |
| " | [21]Robt. Cuthbert, killed. | " | W. A. Pyke, killed. |
| Lieutenant | Charles Barrington, wounded. | " | John George, wounded. |
| " | T. F. Wray, killed. | Adjutant James Hay. | |
| " | T. Hartley, wounded. | Quarter-Master John Hogan. | |
| " | R. F. Fowler, killed. | Surgeon Wm. Armstrong. | |
| " | H. R. Wallace. | Assistant-Surgeon Martin Mahony. | |
| " | T. Y. Lester, wounded. | " | William Williams. |
| " | R. Knowles, wounded. | ||
| " | Honourable F. Russel, wounded. | ||
| Officers. | Serjeants. | Drummers. | Rank & File. | Total. | |
| Killed | 7 | 2 | .. | 57 | 66 |
| Wounded | 11 | 12 | .. | 143 | 166 |
| —— | —— | —— | —— | —— | |
| Total | 18 | 14 | .. | 200 | 232 |
From Estremadura the Royal Fusiliers retraced their steps to the Agueda, and the army, advancing into Spain in June, drove the French from Salamanca. The inhabitants of this city illuminated their houses, shouted, sang, and wept for joy as the British troops took up a position on the mountain of St. Christoval, about five miles in advance; at the same time the forts (fortified convents) at Salamanca were besieged.
The French general, Marmont, advanced with a powerful army, and a series of manœuvres followed; but he was unable to relieve the forts, and they fell into the hands of the allies towards the end of June, when he withdrew beyond the Douro, followed by Lord Wellington.
On the night of the 16th of July the Royal Fusiliers marched to Castrejon, to which place the fourth and light division and a brigade of cavalry proceeded, preparatory to the assembling of the army on the Guarena; but the French commander, having been reinforced, passed the Douro, and attacked the troops at Castrejon on the morning of the 18th of July. Some sharp skirmishing occurred, and the Royal Fusiliers had two men killed and fourteen wounded; but this small body of British, being opposed to the whole French army, withdrew behind the Guarena. A series of manœuvres brought the allied army back to the position of St. Christoval, in front of Salamanca, in the vicinity of which city the two armies confronted each other on the 22nd of July.