[citation needed] Thanks to the signing of the Treaty of Adrianoupolis (Edirne) on September 2, 1829, that unfettered the Danube grain trade, Sulina, by then under Russian control, became an important port.

One of the treaty's terms determined the establishment of the European Commission of the Danube (CED), which would conduct infrastructure works on the mouth of the river in order to make it navigable for larger ships as well.

The technical works allowed entrance to the Danube for a great number of "foreign", i.e. non-Greek ships, leading to a higher level of competition.

[6][7] This was probably caused by an encounter with the Romanian torpedo boat Smeul, whose captain surprised a German submarine near Sulina in November 1916, the latter reportedly never returning to her base at Varna.

[8] In World War II, the Soviet M-class submarine M-59 was sunk by mines laid off Sulina by the Romanian minelayers Amiral Murgescu, Regele Carol I and Dacia.