Napoleon attempted a forced crossing of the Danube near Vienna, but the French and their allies were driven back by the Austrians under Archduke Charles. The battle was the first time Napoleon had been personally defeated in over a decade. However, Archduke Charles failed to secure a decisive victory as Napoleon was able to successfully withdraw most of his forces. The French lost over 20,000 men including one of Napoleon's ablest field commanders and close friend, Marshal Jean Lannes, who died after being mortally wounded by an Austrian cannonball in an attack on Johann von Klenau's force at Aspern, which was backed up by 60 well-placed guns. The victory demonstrated the progress the Austrian army had made since the string of catastrophic defeats in 1800 and 1805.