1708
After landing at Lisbon, the regiment marched under the orders of its colonel, the Earl of Barrymore, to the Alemtejo; in the spring of 1708 it was encamped at Fuentes de Sapatores, between Elvas and Campo Mayor, with the army commanded by the Marquis de Fronteira, and was formed in brigade with the regiments of Stanwix and Galway (newly-raised corps, afterwards disbanded) under Brigadier-General Thomas Pearce (of the fifth foot); but the services of the Thirteenth were limited to operations of a defensive character.
1709
In April, 1709, the regiment was encamped near Estremos, from whence it was removed to Elvas, and subsequently to the banks of the Caya. On the 7th of May, the French and Spaniards under the Marquis de Bay marched in the direction of Campo Mayor, when the Portuguese generals resolved to pass the Caya and attack the enemy, contrary to the advice of the Earl of Galway. The Portuguese cavalry of the right wing crossed the river, and opened a sharp cannonade; but when the opposing horsemen advanced to charge, the Portuguese squadron galloped out of the field, leaving their cannon behind. The infantry of the allied army stood its ground, repulsed the charges of the Spanish cavalry three times, and afterwards commenced its retreat, when the Earl of Galway led forward the Thirteenth, Stanwix’s, and his own regiment, to favour the retrograde movement. The Thirteenth were in front, and charged the Spaniards with distinguished gallantry; the other two regiments of the brigade also evinced great bravery, and the three corps overthrew the leading columns of the opposing army, and recaptured the Portuguese guns. Animated and encouraged by this success, the three regiments pressed forward until they became exposed to the attack of superior numbers, when the Portuguese cavalry of the left wing were ordered to support them, but instead of obeying these orders, the Portuguese squadrons galloped to the rear. Thus forsaken, the three regiments were cut off from the allied army, surrounded by opponents, and only a few officers and men were able to cut their passage through the host of adversaries which environed them; the remainder were forced to surrender prisoners of war. Among the prisoners were Major-General Sankey and Brigadier-General Thomas Pearce.
The Thirteenth foot sustained a severe loss on this occasion; besides the killed and wounded, it had Colonel the Earl of Barrymore, four captains, eight lieutenants, eight ensigns, three volunteers, and between two and three hundred non-commissioned officers and soldiers taken prisoners.
1710
The captured officers and soldiers were exchanged; and the regiment served the campaign of 1710 on the frontiers of Portugal, but had no opportunity of distinguishing itself.
1711
1713
In 1711 the Thirteenth foot were withdrawn from Portugal, and proceeded to Gibraltar, where they were stationed until the peace of Utrecht, 1713, when that fortress was ceded to Great Britain.
At the conclusion of the peace, 1713, the regiment received drafts of non-commissioned officers and soldiers from several corps which were ordered to be disbanded, and the protection of the important fortress of Gibraltar was confided to the fifth, Thirteenth, and twentieth regiments.