In April 1689 he sailed under his father on La Railleuse, escorting a munitions convoy to Brest, accompanied by Claude de Forbin.

Forbin relates that when the engagement began, Jean Bart thought his son showed a sign of fear, and tied him to the main mast for the duration of the fight to accustom him to defying danger.

[3] François Cornil dissociated himself from a cousin named Jean Bart, a simple sailor, before his father died on 27 April 1702 .

As he rose in the navy he cut his ties with his cousins, who were tailors, coopers, carpenters, sailors and fishmongers, and tried to behave as a true gentleman.

[3] He was second in command to Forbin on 2 October 1706 in a fierce battle near Hamburg when the French took many merchantmen escorted by six Dutch vessels.

Bart, then one of the oldest captains, was raised to the rank of chef d'escadre on the recommendation of Louis Jean Marie de Bourbon, Duke of Penthièvre, Admiral of France.