Ruhr (rŏr) [key], region, c.1,300 sq mi (3,370 sq km), W Germany; a principal manufacturing center of Germany and formerly known as one of the world's greatest industrial complexes. In the 1980s the coal and steel industries declined, leading to serious unemployment. By the 1990s, more than three fifths of the working population came to be employed in the service sector. The Ruhr lies along, and north of, the Ruhr River (145 mi/233 km long), which rises in the hills of central Germany and flows generally west to the Rhine River at Duisburg. The Ruhr's principal cities are, in the west, Duisburg, Mülheim, Essen, Oberhausen, Bottrop, Gladbeck, and Gelsenkirchen; and in the east, Bochum, Dortmund, and the smaller cities of Wattenscheid, Recklinghausen, Herne, and Witten. Extensive coal deposits, especially the high quality coking coal required in steel manufacturing, underlie the region in basins that are near the surface along the Ruhr River (where the oldest mines and steel plants are located), and at greater depths to the north along the Lippe River (where most of the modern mines are found). Many coal deposits in this region have been exhausted. Iron ore, oil, chemicals, and other raw materials are imported into the region by way of the Rhine, the Ruhr (navigable below Witten), the Rhine-Herne Canal, the Dortmund-Ems Canal, and a dense network of rail and road connections. The Ruhr Planning Authority (est. 1921) protects designated farmlands and green areas from encroachment by the cities and enforces pollution legislation. The development of the Ruhr district began in the 19th cent. when the Krupp and Thyssen concerns built large integrated coal and steel empires. The Ruhr was occupied (1923) by French and Belgian forces during the dispute over reparations. The troops evacuated (1925), but the occupation greatly embittered German nationalist feeling. Some of the chief Ruhr industrialists helped Hitler to power in 1933. The Ruhr, which was vital in the production of armaments for the German military, was a major bombing target for Allied forces during World War II. About three fourths of the region was destroyed; nearly a third of the area's coal mines were forced to close down. The International Authority for the Ruhr was set up in 1949 with responsibility for development of the region. Control passed to the European Coal and Steel Community in 1952 and to West Germany in 1954. Coal production has suffered from competition from other fuels, but the overall industrial strength of the region is greater now than prior to 1945. In the creation of the new state of North Rhine–Westphalia in 1946, the provincial border between Westphalia and the Rhineland was removed, improving the integration of operations in the region.