ARGONNE, a wooded plateau of north-east France, forming a natural barrier between Lorraine and Champagne, and includ ing portions of the departments of Ardennes, Meuse, and Marne. The Argonne, S.S.E. to N.N.W., is 44m. long with an average breadth of iom. and an average height of I,' soft. It connects the plateaus of the Haute Marne and the Ardennes. The valleys of the Aire and other rivers traverse it longitudinally, a fact to which its importance as a bulwark of north-east France is largely due. On the east the plateau forms a line of rocky bluffs overlooking the plain of the Barre and the Aire gorge, but westwards it slopes gently towards the Aisne. The chief forest, the "Argonne," ex tends for 25m. See MEUSE-ARGONNE OPERATIONS.