Early in August 1792 Parisians learnt of a manifesto issued by the commander-in-chief of the Prussian armies, the Duke of Brunswick. Its language provoked both anger and resolve, threatening as it did summary justice on the people of Paris and the destruction of their city if Louis and his family were further harmed or threatened. The threat added to the popular conviction that Louis and Marie-Antoinette were complicit in the defeats being suffered by the army.
…His Majesty the King of Prussia with His Imperial Majesty, through the ties of a close and defensive alliance, and himself a preponderant member of the Germanic body, could thus not refrain from going to the aid of his ally and of his co-State; and it is under this double relationship that he takes up the defence of this monarch and of Germany.
To these major interests is joined yet another equally important goal, and one which is close to the heart of the two sovereigns, that is, to have the anarchy within France cease, to stop the attacks being made on the throne and the altar, to re-establish legal power, to return to the king the safety and freedom of which he is deprived, and to place him in a position to exercise the legitimate authority which is his due.
Convinced that the healthy part of the French nation abhors the excesses of a faction that subjugates it, and that the majority of the population waits impatiently for the moment of aid to openly declare themselves against the odious enterprises of their oppressors, His Majesty the emperor and His Majesty the king of Prussia call on them and invite them to return without delay to the voice of reason and justice, of order and peace. It is with this in view, that I the undersigned, commander general in chief of the two armies, declare:…