Born in Reims, France, du Coudray entered the French military and trained as an artillery specialist.
[1] Well connected to the French court (he once tutored the future Charles X on military affairs), du Coudray was a leading proponent of the Gribeauval system of artillery in the Seven Years' War.
In 1776, the American diplomat Silas Deane came to France to recruit skilled military talent, particularly engineers, for the colonial cause.
[2] Impressed by du Coudray, whom he described as the "first engineer" of the French military establishment, Deane agreed to hire du Coudray into the Continental Army with the rank of major general and command of the Continental Army's artillery and engineering corps.
A number of American generals were outraged that high ranks were awarded to foreigners, and the Continental Army's artillery chief, Henry Knox, was particularly incensed that du Coudray would outrank him.
To placate Knox, who threatened to resign over the matter, and to resolve conflicts of command and personality issues between du Coudray and another French engineer, Louis Lebègue Duportail, du Coudray was not assigned to a command position, and was instead appointed as "Inspector General of Ordnance and Military Manufactories" in August 1777.