The allies represented a population of ninety millions. The realms of Frederick embraced scarcely five millions of inhabitants. The allies decided that they would no longer make an exchange of prisoners. It was manifest that, by merely protracting the war, even without any signal successes on the part of the allies, Frederick would find all his resources of men exhausted. Frederick, who was never very scrupulous with regard to the means which he employed for the promotion of his ends, immediately compelled his prisoners of war, of whatever nationality, to enlist in his service.

Voltaire promptly replied to this letter in corresponding terms of flattery. His letter was dated Cirey, August 26th, 1736: