Lieut.-Colonel Pack afterwards marched into Spain, under Lieut.-General Sir John Moore, and was at the affair of Lugo on the 5th of January 1809, and at the battle of Corunna on the 16th of that month, after which he returned to England, and embarked in July following for Holland, under Lieut.-General the Earl of Chatham. On landing at Walcheren, Lieut.-Colonel Pack was appointed to command a small corps of cavalry and light infantry; was employed in the siege of Flushing, and particularly named by Lieut.-General Sir Eyre Coote for the command of a detachment to storm an advanced work on the right of the enemy’s line. These orders were successfully executed, the detachment taking forty-nine prisoners, and spiking the guns, though defended by five times the number of men under Lieut.-Colonel Pack. After the surrender of Flushing he was appointed commandant of Ter Veer, where he was dangerously ill for a short period, but remained until the island was evacuated, on which occasion, in conjunction with Commodore Owen, he commanded the rear-guard of the army. Soon after the return of the SEVENTY-FIRST to England, in December 1809, the battalion was prepared again for active service; but the government did not consider the men had sufficiently recovered from the effects of the Walcheren fever. Lieut.-Colonel Pack, being extremely anxious to bear a part in the momentous campaign about to commence in the Peninsula, obtained His Majesty’s permission to proceed to Portugal, and offer his services to Viscount Wellington and Marshal Beresford. Both generals having decided that he could not be more usefully employed than with the Portuguese troops, he accepted an infantry brigade in that service, and took the command of it just before the siege of Ciudad Rodrigo by Marshal Massena, previously to his invasion of Portugal. On the 25th of July 1810 Lieut.-Colonel Pack was appointed aide-de-camp to the king, with the rank of colonel in the army. After the surrender of Ciudad Rodrigo, of Almeida, and Marshal Massena’s passage of the Coa, Colonel Pack’s brigade (an independent one) was directed to take a separate route with a regiment of cavalry attached to it, and remained in presence of the enemy’s army at St. Combadoa, retiring slowly before it, on his advance to the position at Busaco. The conduct of the brigade was noticed in that battle, which was fought on the 27th of September 1810. In the admirable retreat afterwards to the lines of Lisbon, it formed, with the light division and cavalry, the rear-guard of the allied army. The first battalion of the SEVENTY-FIRST having at that period joined Viscount Wellington, Colonel Pack’s wish was to have returned to the battalion, but by the desire of both commanders-in-chief, he continued to serve in the Portuguese army.