Decrès was born in Châteauvillain, Haute-Marne on 18 June 1761 and joined the Navy at the age of 18, in the squadron of Admiral De Grasse.
When king Jan III Sobieski distanced himself from France, and allied with Austria, he was accused of treason and emigrated to France in 1683, where he assumed the title of comte de Châteauvillain and spent the last years of his life as a royal secretary.