|The Austrians took advantage of Napoleon's preoccupation with the Peninsular War, to make preparations to attack the French. In April 1809 Archduke Charles appealed to the German nation to embark on a war of liberation. His appeal was mostly unheeded, but he continued his invasion of Bavaria with an army of 170,000. Napoleon hurried back from Spain and drove the Austrians back. On May 13th Napoleon occupied Vienna. His initial victory was short-lived and he was soon forced to withdraw across the Danube after his defeats at the battle of Aspern and Essling.