He made the acquaintance of Silas Deane, one of the most unscrupulous of the American agents, who promised him, though he was only twenty years of age, the rank of major-general.

As he was at all times the slave of a most overweening conceit, he was tempted by that bait; and, though he could not leave France without incurring the forfeiture of his military rank in the army of his own country, in April, 1777, he crossed over to America to serve as a volunteer under Washington, who naturally received with special distinction a recruit of such political importance.

He was present at more than one battle, and was wounded at Brandywine; but the exploit which made him most conspicuous was a ridiculous act of bravado in sending a challenge to Lord Carlisle, the chief of the English Commissioners who in 1778 were dispatched to America to endeavor to re-establish peace.

However, the close of the war, which ended, as is well known, in the humiliation of Great Britain and the establishment of the independence of the colonies, made him seem a hero to his countrymen on his return.

The queen, always eager to encourage and reward feats of warlike enterprise, treated him with marked distinction, and procured him from her husband not only the restoration of his commission, but promotion to the command of a regiment;[6] kindness which, as will be seen, he afterward requited with the foulest ingratitude.
Nor was this most imprudent war with England the only question of foreign politics which at this time interested Marie Antoinette.