 Complete the following phrase:  The opera is a pièce de circonstance a work written for a special occasion intended to arouse French patriotism during the Campaign of France when Allied armies were invading the country, intent on defeating Napoleon. Amaury Duval, the Inspecteur des Beaux-Arts, encouraged such propaganda works, writing to the Interior Minister: The police have ordered pièces de circonstance to be composed and played in every theatre in Paris. Its a bit of a hackneyed way of arousing enthusiasm; but we must neglect nothing at such a critical conjuncture. The opera compares Napoleon to Charles Martel, who defeated the attempted Muslim invasion of France at the 