In early July 1809 Napoleon crossed the Danube with 187,000 men to confront the Austrian Archduke Charles and an army of 145,000 men. The fighting that followed dwarfed in intensity and scale any previous Napoleonic battlefield, perhaps any in history: casualties on each side were over 30,000. The Austrians fought with great determination, but eventually the Emperor won a narrow victory. It had not been his finest battle, however: the day was carried more by firepower (French artillery fired over 71,000 rounds) and bludgeoning than anything else. Wagram was decisive in that it compelled Austria to make peace. It also heralded a new, altogether greater order of warfare, anticipating the massed manpower and weight of fire deployed much later in the battles of the American Civil War and then at Verdun and on the Somme. This significant battle has rarely been analysed in any detail. Most of the current literature on it is French and self-serving. Gunther Rothenberg will tell for the first time the story of this immense engagement from both sides, making use of both French sources and the extensive Austrian archives.