has more open space, and its valleys normally can be traveled. A single river, the Alzette, bisects this part of Luxembourg in a north-south course which takes it through the capital city. But the eastern approach to the Good Land erases much of its military attractiveness. Between Sierck and Wasserbillig the Moselle River forms the boundary between Luxembourg and Germany. In this sector the left or Luxembourg bank of the river is especially difficult even by comparison with the normal terrain obstacles encountered in the High Ardennes. Farther north, where the Sauer River continues the boundary, the river valley is somewhat less formidable but is backed up by a broken, gorge-riven area in the neighborhood of Echternach known as the "Luxembourg Switzerland."
It is natural, with the Ardennes mass forming a northeast-southwest divide between the tributaries of the Meuse and the Moselle and with rugged geological patterns twisting and turning these tributaries, that the military hydrography of the Ardennes should be important. The prolongation of the Ardennes in northern Luxembourg is dissected by four rivers. On the eastern frontier the Our River continues the boundary trace begun by the Moselle and the Sauer. In the interior the Wiltz, the Clerf, and the Sure divide the country into water-bound compartments. Their valleys are long and narrow, so narrow and tortuous that they cannot be followed by roads. They are further complicated by "cups" scoured out of the side walls and by cross ravines, deep and narrow.
In the Ardennes north of Luxembourg it is possible to cross from Germany into Belgium without traversing a major stream. About twenty miles west of the frontier, however, comes the first of the rivers descending from the High Ardennes into the Meuse; these are the Ambleve and the Salm which serve as flankers for the swamp-encrusted table-land of the Hohes Venn and must be crossed in any movement west from St. Vith, Malmedy, or Spa. Next comes the longest of these rivers, the Ourthe, which is the most severe military obstacle east of the Meuse. It originates west of Bastogne as a small creek, then meanders north until it meets the Meuse at Liege. At Ortheuville the Ourthe begins to cut through a narrow and winding defile with steep, rocky sides fringed by pine trees. Just north of La Roche the Ourthe leaves its tortuous canyons and enters the Famenne Depression. That part of the course between Ortheuville and La Roche permits no road adjacent to the river bed; all approaches to the east-west crossing sites are difficult. Just east of the defile through which flows the middle Ourthe lies the Plateau des Tailles, which rises to over 1,800 feet at the Baraque de Fraiture. Two rivers are found between the Ourthe and the Meuse: the Lesse and L'Homme whose confluence is near Rochefort. Neither of these rivers is too difficult of negotiation, but the main westward crossing for movement toward Dinant and the Meuse centers at Rochefort. At the very edge of the Ardennes in the southwest is the Semois River, which wends its way westward from Arlon to the Meuse. The Semois is deeply sunk through much of its course, flowing between steep walls which descend directly to the water's edge and so deny space for road or rail on the valley bottom Although the rivers of the Eifel, as dis-