Meuse (myōz, Fr. möz) [key], Du. Maas, river, c.560 mi (900 km) long, rising in the Langres Plateau, NE France and flowing N past Sedan (the head of navigation) and Charleville-Mézières into S Belgium. It is joined by the Sambre River at Namur. From Namur the Meuse winds eastward skirting the Ardennes, passes Liège, and turns north, where it forms part of the Belgian–Dutch border before swinging westward through SE Netherlands (where it is called the Maas). Near 's Hertogenbosch it branches out to form a common delta with the Rhine River. One branch joins with the Waal River near Gorinchem to form the Merwede River, which flows into the North Sea. The other branch, called the Bergsche Maas, flows into an inlet of the North Sea S of Dordrecht. The Oude Maas (Old Meuse), which is a branch of the Waal, and the Nieuwe Maas (New Meuse), which is a continuation of the Lek River, actually belong to the Rhine estuary. The Meuse is linked with the Belgian port of Antwerp by the Albert Canal and with Rotterdam and other Dutch ports by the intricate system of Dutch waterways; thus it is one of the chief thoroughfares of Europe. The Belgian section of the Meuse valley, especially around Namur and Liège, is an important industrial and mining region. A strategic line of defense, particularly in Belgium and France, the valley has been a battleground in many wars, and most of the cities along its course have been strongly fortified since the Middle Ages.