Nazi rule over the Danube River was brought about by force of arms, through annexation of Austria, invasion of Yugoslavia and of the Soviet Union and treaties with the Kingdom of Romania and Hungary, but a legal cover was provided through moves that resulted in a new international order on the river beginning in 1940 and ending in 1945.
Before World War II, international trade and commerce at the mouths of the Danube, 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, the United Kingdom, and Italy, the chief commercial nations of Europe at that time. Upstream of Brăila, the river was under the control of the International Danube Commission, a body composed only of the riparian states.
From 1938 through 1940 the regimes of both commissions were broken, and Nazi Germany assumed control of the Danube through a series of moves which were ignored by the victorious Allies after the war.
Romania had desired the outright abolition of the Danube River Commission since 1881, when King Carol I said he would insist on the mouths of the Danube, which ran through Romanian territory, being "exclusively controlled by Romanian officials." The country renewed its demands in 1919 at the Paris Peace Conference and in 1921 at a conference at which the Danube River Commission was renewed and strengthened as an independent agency.
By 1935, a new power had appeared through the 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."
The demise of the old European Commission of the Danube as a semi-independent agency in the affairs of Europe took place with startling suddenness in August 1938.