A war in Look to the West.
With the death of Augustus III (Frederick Augustus II of Saxony), the Polish-Lithuanian throne became vacant and the deadlocked Sejm, unable to pick a candidate, resulted in minor civil war. The great powers intervened, with Russia now having the Germanophile Tsar Peter III at the helm. Russia and Prussia united, bought Swedish neutrality by promising Sweden Courland, and defeated the Austrians and their minor German allies.
The Treaty of Stockholm ended the Polish-Lithuanian Commonwealth, breaking it into its component parts. The thrones of a reduced Kingdom of Poland and Grand Duchy of Lithuania were given to the King in Prussia and the Tsarevich of Russia respectively, while pieces carved off of both were directly absorbed into Prussia and Russia. Krakow was thrown as a bone to Austria.