In the hardships and horrors of that midwinter retreat young Campbell bore his share. Little, if any fighting came in his way, since the division to which his battalion belonged was for the most part in front. During the retreat it experienced a loss of one hundred and fifty men; but they are all specified as having died on the march or having been taken prisoners by the enemy. Nor had it the good fortune to take part in the battle of Coruña, having been stationed in the town during the fighting. There fell to a fatigue party detailed from it the melancholy duty of digging on the rampart of Coruña the grave of Moore, wherein under the fire of the French guns he was laid in his "martial cloak" by his sorrowing Staff in the gray winter's dawn. Beresford's brigade, to which Campbell's battalion belonged, covered the embarkation and was the last to quit a shore of melancholy memory. General Shadwell writes that, "To give some idea of the discomforts of the retreat, Lord Clyde used to relate how for some time before reaching Coruña he had to march with bare feet, the soles of his boots being completely worn away. He had no means of replacing them, and when he got on board ship he was unable to remove them, as from constant wear and his inability to take them off the leather had adhered so closely to the flesh of the legs that he was obliged to steep them in water as hot as he could bear and have the leather cut away in strips--a painful operation, as in the process pieces of the skin were brought away with it."
After a stay in England of little more than six months Campbell's battalion was again sent on foreign service, an item of the fine army of forty thousand men under the command of the Earl of Chatham. The main object of the undertaking, which is known as the Walcheren Expedition, whose story occupies one of the darkest pages of our military history, was to reduce the fortress of Antwerp and destroy the French fleet lying under its shelter, in the hope of disconcerting Napoleon and creating a diversion in favour of Austria. But opportunities were lost, time was squandered, and the expedition ended in disastrous failure. Montresor's brigade, to which Campbell's battalion belonged, disembarked on the island of South Beveland in the beginning of August, to be the gradual prey of fever and ague in the pestilential marshes of the island. Nothing was achieved save the barren capture of the fortress of Flushing; and towards the end of September most of the land forces of the expedition, including Campbell's battalion, returned to England. Over one-sixth of the original army of forty thousand men had been buried in the swamps of Walcheren and South Beveland; the survivors carried home with them the seeds of the "Walcheren fever," which affected them more or less for the rest of their lives. Colin Campbell was an intermittent sufferer from it almost if not quite to the end of his life.