 When the British occupied Philadelphia in September 1777, Duché was arrested by General William Howe and detained, underlining the seriousness of his actions.He was later released, and emerged as a Loyalist and propagandist for the British, at which time he wrote a famous letter to General George Washington, camped at Valley Forge, Pennsylvania, in which he begged him to lay down arms and negotiate for peace with the British.Suddenly, Duché went from hero of the Revolutionary cause to outcast in the new United States.