By the end of the Thirty Years' War, the Austrians had built a fortress on the island to secure the southwestern border of the Breisgau. In 1678, French troops sent by François de Créquy fired at the city. In 1745, during the War of the Austrian Succession, the French made a fortress on the same ground and also ruined part of the city wall. On 17 July 1796, Rheinfelden was again occupied and looted by the French.