By 1935, Charlotte had sold her German properties, the former residential palaces of the Dukes of Nassau, Biebrich Palace and Schloss Weilburg, to the State of Prussia. During World War II the grand ducal family left Luxembourg shortly before the arrival of Nazi troops. Luxembourg's neutrality was violated on 9 May 1940, while the Grand Duchess and her family were in residence at Colmar-Berg. That day she called an extraordinary meeting of her leading ministers, and they all decided to place themselves under the protection of France, described by the Grand Duchess as a difficult but necessary decision. Initially the family took up residence at the Château de Montastruc in south-western France, but the rapid advance of the German forces into France followed by French capitulation the next month caused the French government to refuse any guarantee of security to the exiled Luxembourg government. Permission was received to cross Spain provided they did not stop "en route", and the Grand Duchess with her ministers moved on to Portugal.