Seven Years%27 War
In 1756 Austria was making military preparations for war with Prussia and pursuing an alliance with Russia for this purpose. On June 2, 1746, Austria and Russia concluded a defensive alliance that covered their own territory and Poland against attack by Prussia or the Ottoman Empire. They also agreed to a secret clause that promised the restoration of Silesia and the countship of Glatz (now Kłodzko, Poland) to Austria in the event of hostilities with Prussia. Their real desire, however, was to destroy Frederick’s power altogether, reducing his sway to his electorate of Brandenburg and giving East Prussia to Poland, an exchange that would be accompanied by the cession of the Polish Duchy of Courland to Russia. Aleksey Petrovich, Graf (count) Bestuzhev-Ryumin, grand chancellor of Russia under Empress Elizabeth, was hostile to both France and Prussia, but he could not persuade Austrian statesman Wenzel Anton von Kaunitz to commit to offensive designs against Prussia so long as Prussia was able to rely on French support.

Q: What Russian-Austrian agreement preceded the Seven Years War that started in 1755-56?
June 2, 1746, Austria and Russia concluded a defensive alliance that covered their own territory and Poland against attack by Prussia or the Ottoman Empire