At the beginning of July 1815, a few days after his defeat at Waterloo, Napoleon abdicated and embarked for his last exile on the island of Saint Helena. At the same time, a million foreign soldiers, from around thirty European nations and states, descended on France and occupied almost the entire territory. Taking advantage of this general cure, Switzerland joined this last anti-Napoleonic coalition and invaded Franche-Comté, leading a brief and easy three-week military campaign. For the last and rare time in its history, the Swiss army entered foreign land and fought French soldiers. Operating jointly with the Austrians, it obtained the capitulation of the castle of Blamont, the fort of Joux and occupied several towns and villages, up to the gates of Besançon. It withdrew its last troops in November 1815, after having also participated in the siege of the fortress of Huningue, in Alsace. Curious and atypical, this anecdotal episode constitutes an interesting and unique page in the military history of the Swiss under the First Empire.