He passed the lieutenant's exam at the beginning of January 1788 but was not promoted until the general round of promotions at the outbreak of the French Revolutionary War in 1793. Hennah had little opportunity for distinction until 1800, when he participated in a boat raid on the Morbihan river in which the French corvette Réloaise was burnt.
He successfully completed his lieutenant's exam at the beginning of January 1788 but wasn't promoted until the widespread promotion round that started with the outbreak of the French Revolutionary War in 1793. Hennah didn't have much opportunity to stand out until 1800, when he participated in a daring boat raid on the Morbihan river where the French corvette Réloaise was destroyed.