The Quadruple Alliance was formed by the monarchist Great Powers of Austria, Prussia, Russia, and Great Britain to counter the military and revolutionary republican political threats posed by the expansion of the First French Empire under Napoleon I and to fight the War of the Seventh Coalition. In the wake of the final defeat of Napoleon at the Battle of Waterloo on 18 June 1815, the alliance was formalized with the signing of the Treaty of Paris on 20 November 1815.