The double title , both Prussian and French , meant that the duc de Sagan was a neutral party in the Second World War . His house ( the ChÃ cents teau de ValenÃ ay ) was a safe place to keep pictures and other things from the Louvre when German soldiers were in France . The double title , both Prussian and French , served to render the duc de Sagan a neutral party in World War II : his ChÃ cents teau de ValenÃ ay provided a safe haven for treasures of the Louvre during the German occupation of France .