Treaty of Neuilly-sur-Seine
After "UB-8" was transferred to the Bulgarian Navy in May 1916, she was renamed "Podvodnik No. 18" (in Cyrillic: "Подводник No. 18"). She was Bulgaria's first submarine, and was engaged primarily in coastal defense duties off Bulgaria's main Black Sea port of Varna. "Podvodnik No. 18" survived the war and was ceded to France after the Treaty of Neuilly-sur-Seine.