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
Before World War II, international trade and commerce at the mouths of the Danube River, as well as many of the physical works needed to keep vessels from running aground, were regulated by an international agency called the European Commission of the Danube, founded in 1856. By the time the Hitlerian invasions began in 1938 the commission was composed of the riparian (river-bordering) states, plus France, Great Britain, and Italy, the chief commercial nations of Europe at that time. Above Brăila, the river was under the control of the International Danube Commission, a body composed only of the riparian states.