In 1807, Napoleon I of France temporarily recreated a Polish state as the satellite Duchy of Warsaw, after a successful 1806 uprising against Prussian rule. In accordance with the Treaty of Tilsit, the duchy was ruled by his ally, Frederick Augustus I of Saxony. The Polish troops and generals aided Napoleon throughout the Napoleonic Wars, particularly those under Józef Poniatowski, who became the only foreign Marshal of the French Empire shortly before his death at the Battle of Leipzig. In the aftermath of Napoleon's exile, Poland was again split between the victorious powers at the Congress of Vienna in 1815. The eastern part was ruled by the Russian tsar as Congress Poland, which temporarily held a liberal constitution. The Prussian-controlled territory of western Poland came under increased Germanization. Thus, in the 19th century, only Habsburg-ruled Austrian Poland and the Free City of Kraków in the south, allowed free Polish culture to flourish.