Occurring at the mid-point in Napoleon’s imperial career, the Franco-Austrian War of 1809, or the War of the Fifth Coalition, highlighted the strengths and weaknesses of the French emperor and his army as well as the beginnings of improvements among their foes. Austria, driven by a desire to avenge previous defeats and hoping to take advantage of Napoleon’s distraction in Spain, opened hostilities by invading Napoleon’s ally Bavaria, but the French emperor hastened to the theater of war, quickly seized the initiative and entered Vienna only one month after departing Paris. The ensuing conflict was fought across a vast geographic canvas. Combat in the principal theater, the Danube valley, featured Napoleon’s first undeniable repulse at Aspern-Essling (21–22 May), the second largest battle of the entire epoch at Wagram (5–6 July) and a surprisingly sudden armistice at Znaim six days later, but the war also encompassed strategically important actions in subsidiary theaters such as Italy, Poland, Hungary, Germany and Holland. It led to Austrian accommodation with France, Napoleon’s marriage to a Habsburg archduchess and eventually to a Franco-Austrian alliance, but it also deepened Franco-Russian suspicions and thus helped set the stage for war in 1812

Building on a comprehensive conscription system established ahead of the French Wars, the Habsburg Monarchy could raise armies almost as large as those available to Revolutionary and Napoleonic France. But fielding a large force was not enough to win. Among the more prominent factors undermining Austria’s military capacity was the collective ethos of her officers, whose meagre pay, low social standing, and limited promotion opportunities bred indifference to military professionalism. While reform efforts by the talented Archduke Charles substantially improved the fighting effectiveness of the Habsburg troops, the Archduke never enjoyed the full trust of the emperor. Against Charles’ advice, in 1805 the army was pushed unprepared into war, resulting in a crushing defeat. In spite of far better military performance in 1809, the Monarchy’s attempt to take on the Napoleonic Empire single-handedly led to another costly failure. Forced to scale down its army in the Peace of Schönbrunn, Austria covertly retained much of its veteran manpower. In 1812, while nominally a French ally, further arrangements were set for a rapid expansion and training of her forces. When the Habsburgs have re-joined the war against Napoleon, the size and quality of the Austrian contingent tipped the balance in favour of the Allied Coalition ensuring Napoleon’s final defeat.