 His business empire began a terminal decline during the Franco-Prussian War (1870–71).Strousberg suffered a first setback after he reached a licence by the Hohenzollern prince Karl Eitel Friedrich, ruler of the Romanian United Principalities as Carol I since 1866, for another railway project bypassing the navigation on the Danube river largely controlled by Austria.The settlement with the Romanian government turned out to be ruinous, as Strousberg, due to several technical and financial difficulties, was not able to fulfil the railway contracts.