 Complete the following phrase:  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 under the command of 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 blasted a portion of the city wall. On 17 July 1796 Rheinfelden was again occupied and looted by the 