 Its commander, Gneisenau, died of cholera (August 1831), and Clausewitz took command of the Prussian army's efforts to construct a "cordon sanitaire" to contain the great cholera outbreak (the first time cholera had appeared in modern heartland Europe, causing a continent-wide panic).Clausewitz himself died of the same disease shortly afterwards, on 17 November 1831.His widow edited, published, and wrote the introduction to his "magnum opus" on the philosophy of war in 1832.