Conway commanded the leading brigade on the American right flank at the Battle of Germantown, and was justly praised for his actions. However, Washington opposed his promotion to Major General, believing that many native American officers with longer and valuable service deserved the rank. This, and Conway's condescending attitude, led to continued friction between the men. Congress appointed Conway a Major General anyway in December of 1777, and made him inspector general of the army.
When his criticism of Washington was used politically, his name was used to describe the infighting known as the Conway Cabal. His role was minor, but he lost his command as a result. He tried a ploy that had worked before his promotion, and submitted his resignation to Congress in March 1778. This time it was accepted so he was forced to leave the army. John Cadwallader shot him in a duel on July 22, 1778. When he recovered, he wrote an apology to Washington and returned to France.
Conway later returned to the French Army and served as governor of French colonies in India. In 1793 he fought with royalist forces in opposition to French Revolution in southern France. Their loss forced him to become an exile from his adopted country, he returned to Ireland remained there until his death in 1800.