The Declaration of Pillnitz, was a statement issued on 27 August 1791 at Pillnitz Castle near Dresden (Saxony) by Frederick William II of Prussia and the Habsburg Holy Roman Emperor Leopold II who was Marie Antoinette's brother. It declared the joint support of the Holy Roman Empire and of Prussia for King Louis XVI of France against the French Revolution. Since the French Revolution of 1789, Leopold had become increasingly concerned about the safety of his sister, Marie-Antoinette, and her family but felt that any intervention in French affairs would only increase their danger. At the same time, many French aristocrats were fleeing France and taking up residence in neighbouring countries, spreading fear of the Revolution and agitating for foreign support to Louis XVI. After Louis and his family had fled Paris in the hopes of inciting a counter-revolution, known as the Flight to Varennes in June 1791, Louis had been apprehended and was returned to Paris and kept under armed guard. On 6 July 1791, Leopold issued the Padua Circular, calling on the sovereigns of Europe to join him in demanding Louis' freedom.