The Russo-Prussian alliance refers to the treaty signed by the Kingdom of Prussia and the Russian Empire on 11 April 1764. It expanded on the Treaty of Saint Petersburg of 1762, which ended the fighting in the Seven Years' War between those two countries. It was a defensive alliance, in which each party declared it would protect the territorial stability of the other. It further allowed both countries to intervene in the Polish–Lithuanian Commonwealth, which was one of the primary intentions of the treaty.