Soon after, Stengel served as a general of brigade in the Army of the North at the Battle of Valmy in September 1792. Still under the command of Charles Dumouriez, he fought at the Battle of Jemappes in November 1792. Later that year, he led Dumouriez's advance guard in successful actions at Mechelen (Malines) and Voroux-les-Liers in the Austrian Netherlands. In March 1793, he was defeated at Aldenhoven and driven out of Aachen by the Allies. For this he was arrested and tried before a Revolutionary Tribunal. He was acquitted but retired from military service.