Socialist Federal Republic of Yugoslavia
Regarding rivers, the Danube was navigable throughout its entire course in Yugoslavia, linking the ports of Belgrade, Novi Sad, and Vukovar with Central Europe and the Black sea. Long stretches of rivers Sava, Drava and Tisza were also navigable.
Nazi rule over the Danube River
Nazi Germany's main concerns in establishing control over the Danubian basin were economic in nature. Adolf Hitler's primary objective throughout the war was to conquer sufficient "living space" ("Lebensraum") at the expense of the Soviet Union in Eastern Europe for German settlement, which would in turn allow control over the country's rich deposits of natural resources (such as oil, grain and iron), transforming Germany into an economic autarky. The Danube was considered to be the main route along which this stream of raw materials was to be transported to Germany proper. Hitler referred to the Danube as the "river of the future". At other times he was more explicit about its role in the German-dominated Europe: