Prince Charles's army was able to return to Bohemia quickly, in good order and at full strength, though it was forced to abandon control of Alsace and Bavaria. Austrian diplomats also persuaded Saxony to re-enter the conflict on Austria's side, though in a strictly defensive role. By early October the Austrians were advancing through southwestern Bohemia toward Prague, while a Saxon army marched from the northwest to support them. Learning of the Austrians' rapid approach and unexpected strength, Frederick began pulling his forces back from south-eastern Bohemia to face the oncoming foes. Frederick tried repeatedly to force a decisive engagement, but Austrian commander Otto Ferdinand von Traun manoeuvred away from all Prussian advances while continually harassing the invaders' supply lines, and the Prussians' supplies ran low in the hostile province. By early November the Prussians were forced to retreat to Prague and the Elbe, and after some weeks of manoeuvre an Austrian–Saxon force crossed the Elbe on 19 November. At this point the Prussians abandoned Prague and gave up Bohemia, retreating in poor morale into Upper Silesia, which they defended through the winter against Austrian incursions. Early 1745: Bavarian defeat On 8 January 1745 Austria further strengthened its diplomatic position with the Treaty of Warsaw, which established a new "Quadruple Alliance" between Austria, Britain–Hanover, Saxony, and the Dutch Republic, aimed at opposing the League of Frankfurt and restoring the traditional borders of the Habsburg Monarchy. Prince-Elector Frederick AugustusII of Poland–Saxony now committed 30,000 troops to the cause in return for cash subsidies from the British and Dutch. This publicly defensive alliance was soon followed by a secret offensive agreement between Austria and Saxony, signed on 18 May in Leipzig, which envisioned a territorial partition of Prussia. Meanwhile, as Austrian forces withdrew from Bavaria to respond to the Prussian invasion of Bohemia, Emperor Charles Albert recovered control of his capital at Munich, only to die shortly after relocating there on 20 January, destroying the rationale behind Frederick's alliance. These events combined to produce a major shift in the direction of the war in Germany. With Prussia's forces driven out of Bohemia, Austria renewed its offensive against Bavaria in March 1745, swiftly over-running the defences that had been reestablished there during the winter. On 15 April the Austrians under Count Batthyány decisively defeated the Franco-Bavarian army at the Battle of Pfaffenhofen and drove the allied forces entirely out of Bavaria. After this