The invaders were soon pressed by want of provisions, and horses died from lack of forage. The great army was therefore obliged to fall back to Berwick without having struck a single effective blow. After this Edward remained inactive at Berwick for eight months, save that he once again crossed the Border and advanced as far as Roxburgh, but only to retreat without having accomplished anything. The Earls of Gloucester and Warrenne reduced the forest of Selkirk and the district, and restored the English power there; while the king's favourite, Piers Gaveston, Earl of Cornwall, went by sea to Perth and tried to reduce the surrounding country, but the Scotch, as usual, retired before him, and he, too, after a time, returned to Berwick. The efforts of the defenders to starve out the invading armies of England were greatly aided by the fact that at this time a great famine raged both in England and Scotland, and the people of both countries were reduced to a condition of want and suffering. Not only did the harvest fail, but disease swept away vast numbers of cattle and sheep, and in many places the people were forced to subsist upon the flesh of horses, dogs, and other animals.