At the end of the brief campaign Campbell was transferred to the first battalion of the Ninth, and had the good fortune to remain under the command of Colonel Cameron, who had also been transferred. In the beginning of October a despatch from England reached Lisbon, instructing Sir John Moore to take command of the British army intended to co-operate with the forces of Spain in an attempt to expel the French from the Peninsula. The disasters which befell the enterprise committed to Moore need not be recounted in detail because of the circumstance that a young lieutenant shared in them in common with the rest of the hapless force. The battalion in which Campbell was serving was among the earliest troops to be put in motion. It quitted its quarters at Quelus, near Lisbon on October 12th, and reached Salamanca on November 11th. When Moore's army was organised in divisions, the battalion formed part of Major-General Beresford's brigade belonging to the division commanded by Lieutenant-General Mackenzie Fraser. On reaching Salamanca Moore found that the Spanish armies which he had come to support were already destroyed, and that he himself was destitute alike of supplies and money. In this situation it was his original intention to retire into Portugal, which might have been his wisest course; but Moore was a man of a high and ardent nature. When on the point of taking the offensive in the hope of affording to the Spaniards breathing-time for organising a defence of the southern provinces, he became aware that French forces were converging on him from diverse points; and on the 24th of December began the memorable retreat, the disasters of which cannot be said to have been compensated for by the nominal victory of Coruña.