In the beginning of September, 1810, the battalion being re-established in health, and numbering 600 rank and file, marched under the command of Lieutenant-Colonel Collins, to join Lord Wellington, at that time retiring to the frontiers of Portugal. It effected its junction with the army the same month, and was placed in the left brigade of the 3rd Division, commanded by General Picton, and in the celebrated division which acquired in the army the distinguished appellation of the “Fighting Division” the 83rd had the honour of serving throughout the remainder of the Peninsular campaigns. With it, therefore, and its heroic commander, Sir Thomas Picton, the services of the battalion in this memorable war are henceforth identified, being engaged in every skirmish, battle, and assault which this renowned division fought and won, and in every glorious deed of daring and honour it was ever so nobly performing. On the 26th and 27th of September the battalion was engaged in the actions on the Sierra de Busaco; but the brunt of the battle falling to the good fortune of the right brigade, its casualties were few, amounting only to 1 lieutenant (Lieutenant Colthurst) and 6 rank and file wounded. For the services of the regiment on this occasion Colonel Collins received a medal, and his Majesty was pleased to sanction the word “Busaco” being borne on its colours and appointments. Shortly after Lieutenant-Colonel Collins was removed to the command of a brigade in the Portuguese service, and the command of the 83rd devolved upon Major H. W. Carr. After the decisive and signal repulse of the French at Busaco, the British army continued its retrograde movement until it was halted by its skilful commander in the strongly fortified lines of Torres Vedras, and the regiment remained in position in these celebrated lines till the month of March, 1811, when the French, under Marshal Massena, commenced its retreat. The British army followed in eager and hot pursuit, and the 3rd Division hanging closely on the rear, the 83rd was in constant and warm engagement with the enemy. It came up with them at Leyria, Pombal, and Condeixa, and in the skirmishes at those places, and at Fleur-de-Lis, Guarda, and Sabugal, its casualties amounted to 2 sergeants and 52 men killed and wounded. In May following, the battalion was actively engaged in the actions at Fuentes d’Onor, on the 3rd, 4th, and 5th of that month, and was mentioned in Lord Wellington’s despatch of the battle, as being distinguished in the defence of the village of Fuentes d’Onor, and the repulse of the enemy therefrom. Its casualties, however, were fortunately but few, amounting to 1 lieutenant (Ferris) and 6 rank and file killed, and 1 lieutenant (Vereker), 1 sergeant, and 22 rank and file wounded, and his Majesty was pleased to sanction the word “Fuentes d’Onor” being inscribed on the colours and appointments of the 83rd, in commemoration of the distinguished conduct of the battalion in that battle.