Sometime before 1907 PD, Jourdain was a People's Commissioner assigned to the light cruiser PNS Vaubon, commanded by Commander Warner Caslet. Vaubon's officers, Commander Caslet included, soon recognized that Jourdain was a fairly decent person in comparison with other People's Commissioners. It was Jourdain who, recognizing the usefulness of Shannon Foraker's technical skills, began to turn a blind eye to the officer's tendency to use pre-revolutionary forms of address. Upon Jourdain's recomendations, other Commissioners who served along Foraker (such as Everard Honeker) also took to ignore her speech lapses. (HH5, HH6, HH7)
Jourdain was present aboard Vaubon during the Fourth Battle of Yeltsin's Star, and still served as Caslet's commissioner when the ship was assigned to Admiral Javier Giscard's Task Force 29 for commerce raiding in the Silesian Confederacy. In Silesia, and after Vaubon's discovery of a ship that had been raided by pirates, Jourdain agreed to endorse Commander Caslet's request to proceed independently in pursuit of the pirates.
Sometime later, Vaubon encountered two pirate ships attacking a Manticoran-flagged merchant vessel in the Schiller System. Upon Commander Caslet's request (which went against his operational orders) to assist the Manticoran ship, Jourdain authorized Vaubon to engage the pirates, an event which would ultimately lead to the cruiser's surrender to the Manticoran ship, which was actually the armed merchant cruiser HMAMC Wayfarer. Along with the rest of the senior officers, Jourdain remained onboard Wayfarer as a "guest" of the Royal Manticoran Navy, and agreed to collaborate with Captain Honor Harrington's efforts to hunt pirate leader Andre Warnecke.
After Wayfarer's loss in the Battle of the Selker Rift and the rescue of her surviving crew by the Manticoran passenger liner RMMS Artemis, and upon the recommendation of Captain Harrington, Denis Jourdain was repatriated to the People's Republic along with Commander Caslet, the remaining senior officers of Vaubon and the surviving crew of the battlecruiser PNS Achmed. (HH6)
Jourdain's reports on Vaubon's senior officers would later go on to help Denis LePic to subtly rehabilitate Warner Caslet in the eyes of State Security, and Everard Honeker to conveniently ignore Shannon Foraker's pre-revolutionary "speech lapses". (HH7)