Argonne, also Argonne Forest, wooded plateau region, north-eastern France, lying between the Meuse and Aisne rivers, and occupying parts of the departments of Ardennes, Marne, and Meuse. The region extends from the Belgian frontier south-east to the vicinity of Verdun, a distance of 71 km (44 mi). It has an average width of about 16 km (10 mi). The Aire River and smaller streams flow through the region. Elevations average about 350 m (1,150 ft), and steep cliffs delineate the river valleys in the eastern part of the region. These, together with woodland and forests, make the region a natural defensive bastion. In 1792, during the French Revolution, the French general Charles François Dumouriez conducted a successful campaign against the Prussians led by Charles William Ferdinand, Duke of Brunswick, on the Argonne; it ended in the decisive French victory of Valmy. In 1870, during the Franco-Prussian War, the Argonne was the scene of the retreat of the French army under Marshal MacMahon from Beaumont to Sedan. The Argonne region was also the site of a major battle of World War I.