Meanwhile, back in Poland, Augustus II continued to reign until he ended his gluttonous life by dying from gangrene after diabetic foot amputation (1733). Stanisław, counting on his son-in-law's support, decided it was a good occasion to try and win back the Polish throne. He travelled incognito back to Warsaw, where he made his sudden appearance on the election field and was chosen – legally, this time – as king of Poland. His earlier coronation was deemed valid, so there was no need to repeat it. However, the history from almost thirty years before repeated itself in reverse – foreign troops, Russian this time around, captured Praga, the eastern suburb of Warsaw, where they arranged a rival election of Augustus II's son, soon afterwards crowned in Cracow as King Augustus III. Stanisław escaped from Warsaw to Danzig (Gdańsk), a city which managed to hold out against a Russian siege for some time. A network of alliances covering Europe transformed the fight for the Polish throne into a major international conflict, which – despite being known as the War of Polish Succession – was fought out mostly in Italy and on the banks of the Rhine. France was quick to capture Lorraine (another border region), but (except a small and unsuccessful landing operation in Westerplatte near Danzig) did little to help Stanisław keep his crown. In the end, Danzig fell and Stanisław, disguised as a peasant, escaped (once again) to Königsberg (now Kaliningrad, Russia).
The war ended with Augustus III staying on the Polish throne; as a consolation prize, Louis XV gave his dad-in-law the Duchy of Lorraine and Bar (1737), where until the end of Leszczyński lived out his days he continued to be years while still being addressed as "king" and where, in the words of Voltaire, he was "able to do more good than all the Sarmatian [that is, Polish] kings ever managed to do on the banks of the Vistula."<ref>{{Cyt
| nazwisko = Voltaire
| inni = trans. Robert M. Adams, ed. Nicholas Cronk