Nicolas-Jean Rouppe was born in Rotterdam, and became a sub-deacon of the order of the Carmelites, but he broke radically with his faith in 1792, the day after Battle of Jemappes between the French revolutionary and Austrian armies on 6 November 1792. That year, he also provoked a riot by destroying the cross in the town hall of Leuven. Under the French occupation he became commissioner of the Dyle department. On 21 July 1803 he received Napoleon at the Castle of Laeken (Laeken).