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
By 1935, a new power had appeared through the entire length of the Danube — Nazi Germany, whose new self-propelled barges swiftly moved up and down the river outside Germany's borders, "the pioneers of the new order. They flew the Swastika and were built of bullet-proof steel."