On 20 April 1792, the Assembly voted to declare war on Austria (Holy Roman Empire). They planned to invade the Austrian Netherlands, but the revolution had made the army weak. Many soldiers deserted. Soon, Prussia joined on the Austrian side. They both planned to invade. Together, on 25 July, they wrote the Brunswick Manifesto, promising that if the royal family was not hurt, no civilians would be hurt in the invasion. The French believed that this meant the king, Louis XVI, was working with the foreign kings. Prussia invaded France on 1 August, 1792. This first stage of the French Revolutionary Wars continued until 1797.