The revolt of Ghent, which broke out the next year, must be considered as the last attempt made by the towns to save their old privileges. For the last time, a Commune raised its head to challenge central power. In spite of the peace of Cadzand, Ghent had succeeded in preserving a privileged situation in the State, and many popular leaders had witnessed with dismay the progress made in 1531 by centralizing tendencies. Beside the defence of local liberties, the aim of the revolutionaries was to restore the situation of the old corporations, which was directly threatened by the economic transformation of the modern regime. Under the new conditions, the "masters" had succeeded in enriching themselves, but the "companions" and prentices had lost all the advantages of the old corporation system. Riots caused by unstable labour conditions had already taken place in Bois-le-Duc (1525) and Brussels (1532). In Ghent, however, the movement acquired more threatening proportions, the magistrates being overwhelmed by the crowd and the workmen seizing the direction of affairs. Charles, who had obtained from Francis I permission to cross France with an army, condemned to torture most of the leaders of the movement, suppressed all the town's privileges by the "Caroline concession" (1540), and even ordered that the well-known bell "Roland" should be unhung. This last punishment remained in the memory of the people as a symbol of the deepest humiliation which might be inflicted on any town. [_TREATY OF VENLOO_] As soon as Charles departed for his expedition to Algiers, the Netherlands were again exposed to the attacks of his enemies, including Francis I, the King of Denmark and the Duke of Cleves, who had inherited the county of Gelder. This time Mary was strongly supported by the States General, and succeeded in facing the attacks on both sides pending the return of the emperor (1543). The latter took the opportunity given him by a prompt victory to settle once for all the Gelder question by the treaty of Venloo. The Duke of Cleves was obliged to renounce all rights over Gelder and Zutphen, which became integral parts of the Netherlands. This was the last act of the work of territorial unification pursued by the dukes of Burgundy. At the same time, in order to protect the Low Countries from French attacks, Charles V fortified the three towns of Marienbourg, Charlemont and Philippeville, called after Mary of Hungary, Charles himself and his son Philip.