In August 1791, the Emperor of Austria and the King of Prussia in the Declaration of Pillnitz threatened revolutionary France to intervene by force of arms to restore the French absolute monarchy. In September 1791, the National Constituent Assembly forced King Louis XVI to accept the French Constitution of 1791, thus turning the French absolute monarchy into a constitutional monarchy. In the newly established Legislative Assembly (October 1791), enmity developed and deepened between a group, later called the 'Girondins', who favoured war with Austria and Prussia, and a group later called 'Montagnards' or 'Jacobins', who opposed such a war. A majority in the Assembly in 1792 however saw a war with Austria and Prussia as a chance to boost the popularity of the revolutionary government and thought that France would win a war against those gathered monarchies. On 20 April 1792, therefore, they declared war on Austria.