The Padua Circular was a diplomatic note produced by Holy Roman Emperor Leopold II on 6 July 1791.  Prompted by the arrest of Louis XVI and Marie Antoinette after the Flight to Varennes , the Circular called on the sovereigns of Europe to join him in demanding their freedom. It was followed by diplomatic initiatives in which the Holy Roman Empire looked for rapprochement with its traditional enemy, Hohenzollern Prussia . 
The Padua circulates with little enthusiasm by the other powers of Europe  so there was no basis for any kind of collective action by the powers on behalf of the French king.
However, it is a convention between Prussia and Austria on July 25, 1791, which is in the process of becoming more controversial, and co-operating over the United Kingdom. The Declaration of Pillnitz , authored jointly by Austria and Prussia, in August 1791 . 
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