This history of the 1809 Franco-Austrian War presents an in-depth chronicle Napoleon's last great victory.   On April 10th, 1809, while Napoleon was occupied in Western Europe with the Peninsular War, the Austrian Empire launched a surprise attack that sparked the War of the Fifth Coalition. Though France would ultimately win the conflict, it would be Napoleon's last victorious war. Even then, the margin of French superiority was decreasing. Archduke Charles, the best of the Habsburg commanders, led a reformed Austrian Army that was arguably the best ever fielded by the Danubian Monarchy.   Though caught off guard, the French Emperor reversed a dire strategic situation with stunning blows that he called his 'most brilliant and most skillful maneuvers'. Following a breathless pursuit down the Danube valley, Napoleon occupied the palaces of the Habsburgs for the second time in four years. He would win many battles in his future campaigns, but never again would one of Europe's great powers lie broken at his feet.   In Thunder on the Danube, historian John H. Gill tackles the political background of the war, including the motivations behind the Austrian offensive. Gill also demonstrates that 1809 was both a high point of the First Empire as well as a watershed, for Napoleon's armies were declining in quality and he was beginning to display the corrosive flaws that contributed to his downfall five years later. His opponents, on the other hand, were improving.